Seedling yellowing leaves and some are dying off. What do you guys think? (with imeages)

Hello I have the following problem.

One of my seedling started to develop these yellow spots. I didn't worry because I wasn't feeding enough based on the nutrient schedule of my fertilizer bottle. I was feeding the "first Root"-strength but already had some true leaves on them so I checked the bottle again and changed the resevoir and fed my plants the amount stated on the fertilizer bottle for plants with first true leaves.

The other seedlings who did not develop the yellow spots were fine with the new nutrient solution and higher EC. But the one with the yellow leaves was stunt and the nutrient EC of her reservoir kept raising a lot (about +0.6EC) so I lowered it again and the next day it has risen again (about +0.3EC) but it has stopped there so I thought everything was ok... some days later still not a lot of growth compared to the other seedlings but as far as I could tell it was not getting worse at least so I thought the problem was gone and she needes some time to recover.

But yesterday the second seedling started to get some of the same yellowing like the first seedling but it was not a lot so I didn't notice it right away. Today the yellowing of the second seedling kept going on and the EC has risen for both again A LOT! the EC was 2.3 again!

Now my first seedling who developed these deficiencies first is very slow growing compared to the other seedlings and is getting worse and worse. And now the second seedling starts to develop the same problems too... And the others keep getting worse too...

I don't really know what the problem is since the EC is raising it looks like they are leeching nutrients in the solution instead of taking them up... I don't really know what was going wrong... Do you know whats happening?

I grow with LED so I use extra Cal/Mag. I use reverse osmosis water. The nutrients I use are general hydroponics TriPart.

The Cal/Mag bottle says to use 0.45EC CalMag. And the GHE TriPart says to add about 0.8-1.2EC for plants with first true leaves.

So I made a nutrient solution with 0.45EC Cal/Mag and 1.2EC GHE TriPart and got about EC1.6

The plants were growing good and fast (but not the first yellow leaves seedling) so I thought I was doing everything right... The EC raised the first day but after that it didn't kept rising and they started to take off. So I just let them stay that way the following days and they kept growing good (not the first yellowing seedling) but yesterday the EC has risen again and today again and now more plants show the same symptoms. Yellowing leaves and the lower leaves start to die on the leave tips... What is going on??

I think they maybe have nutrient lockout so I am flushing the system right now! After that I want to reintroduce the nutrient strength for first true leaves... Maybe the first yellowing seedling had nutrient lockout and since I didn't flush it she was still damaged... What do you think?

Should I have changed the res everytime the EC has risen so much? Maybe some of the nutrients were already used up but the EC was high because of some other nutrient leeching from the first seedling? I don't really know...

I'm reading the nutrient deficiency guide over and over again but I don't know whats going on here and I dont want to make things worse! Maybe they are too big by now and already need the vegetation feeding schedule instead of the first true leaves schedule... Maybe it's a Cal/Mag deficiency... Maybe Nitrogen... Maybe they have nutrient lockout... I don't know it's too much information for me right now.

Infos of the system:

Growlight LED
Hydro DWC
Feeding like the bottle says EC1.6 (1.2 nutrients GHE TriPart and 0.45 Cal/Mag)
PH 5.5-6.5

Here are some pictures (look how small seedling1 is compared to seedling2 who developed the deficiencies just yesterday until then it was groing good!):

Very slow growing Seedling1 from the top (developed the deficiencies 1 week or more ago):


Very slow growing Seedling1 yellowing deficiencie:


Very slow growing Seedling1 dying lower leaves:


Seedling2 from the top:


Seedling2 yellowing leaves:


Seedling2 dying lower leaves:

1.2 EC is too high for that size plant.. Cut it in half .6 EC. As a general rule use half of mfg suggested amounts..

HydoDan said:

1.2 EC is too high for that size plant.. Cut it in half .6 EC. As a general rule use half of mfg suggested amounts..

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Ok so maybe EC was too high and the plant got a nutrient lockout? So flushing now is right and after that I should lower the EC to half the manufacturer recommendation? So as u said EC 0.6 after flushing is done?

How many days to flush? I am using a flushing solution like the GHE Flora Kleen.

What's there to flush? Dump it and refill with a lower ec. Toss the FloraKleen in the trash.

xtsho said:

What's there to flush? Dump it and refill with a lower ec. Toss the FloraKleen in the trash.

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I thought you should flush if there is a nutrient lockout. And since the EC was so high I think I might have a nutrient lockout.

RookieMuffin said:

I thought you should flush if there is a nutrient lockout. And since the EC was so high I think I might have a nutrient lockout.

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You're hydro not soil. If your ec was to high changing the nutrient solution is all you need to do. If you're using the GH 3 part and mixing it in the proper ratios you are not going to have any issues unless you're overfeeding.

"The overfeeding of any plant food can cause nutrient deficiencies"

xtsho said:

You're hydro not soil. If your ec was to high changing the nutrient solution is all you need to do. If you're using the GH 3 part and mixing it in the proper ratios you are not going to have any issues unless you're overfeeding.

"The overfeeding of any plant food can cause nutrient deficiencies"

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OK thank you! I will stop the flush.

When I dump the res now and refill it with a fresh 0.6EC (+0.45 Cal/Mag) and tomorrow the EC has risen again what should I do? Dump again and refill with a fresh 0.6EC (+0.45 Cal/Mag) until it doesn't rise anymore?

RookieMuffin said:

OK thank you! I will stop the flush.

When I dump the res now and refill it with a fresh 0.6EC (+0.45 Cal/Mag) and tomorrow the EC has risen again what should I do? Dump again and refill with a fresh 0.6EC (+0.45 Cal/Mag) until it doesn't rise anymore?

Click to expand...

Something's going on in your process. It shouldn't rise 0.6 ec in a day.

xtsho said:

Something's going on in your process. It shouldn't rise 0.6 ec in a day.

Click to expand...

Hmm ok strange why it was going up that much... I will see this time...

I have dumped the flush and did what you said. Plus I changed the res.

Now I have a fresh res with EC 1.0 (0.6 EC of nutrients which is 50% of the recommended dosage for first true leave plants and 0.45 EC Cal/Mag). The PH of the solution is 5.5 now.

I will measure PH and EC in about 12 hours and see how it is going!

Thank you both for your help I will update later.

RookieMuffin said:

Hmm ok strange why it was going up that much... I will see this time...

I have dumped the flush and did what you said. Plus I changed the res.

Now I have a fresh res with EC 1.0 (0.6 EC of nutrients which is 50% of the recommended dosage for first true leave plants and 0.45 EC Cal/Mag). The PH of the solution is 5.5 now.

I will measure PH and EC in about 12 hours and see how it is going!

Thank you both for your help I will update later.

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I think you're using too much calmag. You're ec shouldn't rise the way you say it does. Something is not right. How are you mixing your nutrients and what are you using to measure the ec? There has to be something going on to cause an ec swing as significant as what you claim is happening.

xtsho said:

I think you're using too much calmag. You're ec shouldn't rise the way you say it does. Something is not right. How are you mixing your nutrients and what are you using to measure the ec? There has to be something going on to cause an ec swing as significant as what you claim is happening.

Click to expand...

Ok I don't know what was going on (the big 0.6EC spike was about a week ago and I don't know what caused it). The last spike went like this: 12/21/2022 1.966EC and PH 6.3 so I've adjusted the PH and then then it was EC 2.120 and PH 5.5 (EC raised because of PH down added). Then 24 hours later 12/22/2022 the EC was 2.306 and PH 6.0 I haven't added anything just waited 24 hours and the EC was up by about 0.2 and the plant problems got worse so I thought I should flush it and start again. I've also opened this thread to ask for help... so I don't know what was going on this time... I don't have the data for the first high spike but doesn't matter I forgot to write all that stuff down but now I keep a diary.

Regarding the calmag... On the bottle it says to add calmag until the EC is 0.45 so I did that. Also when I google it there are a lot of people who recommend to use a EC of 0.4 for calmag... but I don't know what is right. I was just listening to other forum posts and what was recommended on the bottle. (as far as I know the Cal/Mag also has extra nitrogen added)

Now to mixing my nutrient solution. I start with reverse osmosis water. EC 0.0 then I add the Cal/Mag until I reach EC 0.45 then I add my 3 Part nutrients one after another. This time I used 50% of the recommended amount for plants with first true leaves. Then my EC was 1.0. Then I measure the PH and adjust down or up to get a PH of 5.5. Thats how I mix my nutrients.

I measure my EC with a TDS Pen. It can show me the PPM or EC but I use the EC option because this is better because of the 500/700 ppm conversion problem. Everyone measures EC the same but with ppm it depends on the conversion used which is not the same for everyone it depends on the conversion the company uses.

I don't know if it will raise this time I will update in 12 hours with what the new reading is but maybe it won't raise that much this time (I hope so!).

This is a little headache inducing.

Just buy some decent soil and water it with good old fashioned water, you’ll be pleasantly surprised with the results.



have you calibrated your pens/meter recently?

I’d foliar feed the calmag and feed your base nutrient as said above, around 0.6 ec.
As they mature don’t exceed 1 - 1.2 ec until the plants shows signs of needing more.

things go wrong fast in DWC, coco is a little more forgiving and you’ll only need the one res.

GreenestBasterd said:

This is a little headache inducing.

Just buy some decent soil and water it with good old fashioned water, you’ll be pleasantly surprised with the results.



have you calibrated your pens/meter recently?

I’d foliar feed the calmag and feed your base nutrient as said above, around 0.6 ec.
As they mature don’t exceed 1 - 1.2 ec until the plants shows signs of needing more.

things go wrong fast in DWC, coco is a little more forgiving and you’ll only need the one res.

Click to expand...

I stick to DWC no soil for me maybe later but now I'll stick to hydro thanks.

I can't calibrate the TDS pen. Only the PH pen. One day I will buy better instruments like BlueLab or something like that. Right now I only have cheap TDS meter.

So making a new res just with the base nutrients? I don't want to foliar feed later in flowering because of mold... now it would be possible but I don't know...

Maybe I should just use base nutrients when it still goes downhill the next days... we will see how it goes. Thanks for the tip!

Completely understand about the soil mate, I said it tongue-in-cheek haha.

no foliar in flower, just from now until you switch your light cycle to 12/12.

if I’m correct, you should be able to buy a cheap calibration solution for you ec pen to double check it’s reading correctly. Even the cheapest ones come with a screwdriver to adjust, but if you really can’t adjust it, just dipping in a solution that you know the ec of will be beneficial even if it’s out.

GreenestBasterd said:

Completely understand about the soil mate, I said it tongue-in-cheek haha.

no foliar in flower, just from now until you switch your light cycle to 12/12.

if I’m correct, you should be able to buy a cheap calibration solution for you ec pen to double check it’s reading correctly. Even the cheapest ones come with a screwdriver to adjust, but if you really can’t adjust it, just dipping in a solution that you know the ec of will be beneficial even if it’s out.

Click to expand...

Haha ok I see... I really love Hydro lol that's why no soil in the near future haha.

Yeah you are right I didn't think about using calibration solution just to check if the meter reads it correctly! I will do that! I will check the pen later again but as far as I know there is no screw to calibrate it. But I will buy the calibration solution just to check if it reads the EC right.

The pen is shit anyway... one time it reads for example EC 1.1 and one second later it reads EC 1.2 and then 1.1 again... I really hate that pen that's why I will buy an expensive meter from a known manufacturer... not a cheap china shit pen. And then I will store it correctly in storage solution and calibrate it often. One expensive PH and EC meter that's on my wishlist lol.

As I've already made a res change 2 hours ago I will not do one again now. I will change it in some days hopefully it will be stable now! Otherwise I will change it and use Cal/Mag as a foliar feed.

But how to feed Cal/Mag in flower when no foliar feeding in flower? Just add it to the res or don't use it at all and risk deficiencies again?

RookieMuffin said:

Regarding the calmag... On the bottle it says to add calmag until the EC is 0.45 so I did that.

Click to expand...

Remember, use half of mfg suggested.. Try .2

HydoDan said:

Remember, use half of mfg suggested.. Try .2

Click to expand...

Yeah some minutes ago I thought the same thing when I remembered and read again that I use base nutrients at 50% but not the Cal/Mag lol... next res will be with 50% of both!

Ok it's about 12 hours later now. I've measured again and here is what I got.

EC 1.1 (was EC 1.0 12 hours ago)
PH 5.9 (was PH 5.5 12 hours ago)

So in about 12 hours the EC has risen by 0.1 EC and the PH was rising. The seedlings were drinking about 100 milliliters in that time. So my water level was sinking. The EC was rising and the PH was rising too. It looks like the plants are drinking more water than eating nutes right?

What would you guys do? Make a new res with 50% of recommended nutes again but this time also as suggested 50% of recommended Cal/Mag (or none at all?) so that im at EC 0.8 (0.6EC Nutes and 0.2EC Cal/Mag) or just leave it as it is?

why dont you just put fresh water in your tank. until the ec stops rasing?
Take out a few Liters of nutes and change it with fresh water. why waste all that nutes when you put a fresh batch yesterday????
then remember your EC and when you make a new batch aim to go there.
some strains i had would eat 800ppm and some 400ppm in flower soo each plant you have to learn what she wants

amneziaHaze said:

why dont you just put fresh water in your tank. until the ec stops rasing?
Take out a few Liters of nutes and change it with fresh water. why waste all that nutes when you put a fresh batch yesterday????
then remember your EC and when you make a new batch aim to go there.
some strains i had would eat 800ppm and some 400ppm in flower soo each plant you have to learn what she wants

Click to expand...

That's what I normally would do. Just top it off with fresh water. But sometimes I ask myself if I should top off with just reverse osmosis water or with reverse osmios water with Cal/Mag added to it but without base nutrients...? Because if I just add fresh water the Cal/Mag would get diluted... What do you think?

And I don't know why it is rising... too much cal/mag or too much base nutrients you know.

This time I was considering a new nutrient solution again because they have recommended to use 50% of Cal/Mag bottle schedule. And they were even recommending not using Cal/Mag at all just foliar feed. Thats why I've asked to dump again and make a new res or if I should leave it like that.

So if I would dump again and make a new solution I would make it the recommended 50% Cal/Mag and 50% base nutrients so that I'm on the right levels/ratios again. The last batch was 100% of bottle recommendation Cal/Mag and 50% of bottle recommendation base nutrients.

The Cal/Mag has extra nitrogen added to it. It's not just Cal/Mag. Maybe thats the problem so theres to much nitrogen in the solution. (https://www.cannagardening.com/calmag-agent)

On my last grows I had cal/mag deficiencies that's why I was adding them right away. I use LED and people need more Cal/Mag when using LEDs. That's what I've read and what happened to me on my last grows.