Light Burn, Nutrients, or Overwatering?

My plants are 2 weeks into flowering, and they have stretched like crazy. The new growth is lighter green than the old growth, but the highest leaf tips seem to be especially yellow. I'm growing in coco/perlite (%15 perlite) and I'm using 170ppm Cal-mag mixed with 450ppm of GH Trio (so a total of about 620ppm). I'm using a 520 watt (true wattage) LED about 20 inches from the top of the plant. Is this light burn? Will the bleached parts ever recover? Or could this be nutrient burn or something else? Ph of nutrients has been kept around 5.8-6.0 throughout the grow.

beepy1 said:

My plants are 2 weeks into flowering, and they have stretched like crazy. The new growth is lighter green than the old growth, but the highest leaf tips seem to be especially yellow. I'm growing in coco/perlite (%15 perlite) and I'm using 170ppm Cal-mag mixed with 450ppm of GH Trio (so a total of about 620ppm). I'm using a 520 watt (true wattage) LED about 20 inches from the top of the plant. Is this light burn? Will the bleached parts ever recover? Or could this be nutrient burn or something else? Ph of nutrients has been kept around 5.8-6.0 throughout the grow.
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How many ml to how much water gives you 170 ppm of cal mag?? Seems like alot to me (the 170) but you dont have a calmag problem. Maybe drop that down to 100ppm if that is how you do it.

Does the 170 seem high to anybody ?????

Ok, that is kind of what they look like I dont see a problem myself. But if that was my grow I counted about 14 stretchy colas, I would bend, (supercrop) all of them straight horizontal towards the outer area of the grow where I could and even out that canopy.

I think I put 2.5ml Cal-Mag per gallon (half the reccomended strength listed on the bottle). Even going into the third week of flower I can still supercrop with no issues? The stems seem pretty thick, which worries me that they may crack during a supercrop. So does the yellow tips of the top leaves look like some "light burn", or you think it's something else?

All your numbers are fine. The cal mag could be a little high but if you are using half the recommended then I would roll with it. I burn leaves all the time and they don't look like yours. Yours look like they are sick from the nutes or PH but your numbers are ok. That's why cocoa and led's are tricky.

beepy1 said:

I think I put 2.5ml Cal-Mag per gallon (half the reccomended strength listed on the bottle). Even going into the third week of flower I can still supercrop with no issues? The stems seem pretty thick, which worries me that they may crack during a supercrop. So does the yellow tips of the top leaves look like some "light burn", or you think it's something else?

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Yes you can supercrop wouldnt wait much longer though. Now is the time to get the plant set up to be left alone. Its like topping without actually topping anything, to even out the canopy to get better light penetration across more plant material.

The yellow tips are nute burn. Considered to signal your close to being at your max ppm's for that plant with that light. So if you had a bigger light the plant would be able to do more and handle more ppm's. In theory anyways some plants are lite feeders some are heavy. My rule I go by is that I dont like to go much past the wattage of light in relation to my ppm;s. Meaning if I had my veg lights set at 500 watts I wouldnt go past 650 with my ppm's. Plant size and health has a lot to do with it to as far as pushing ppm's.

Think balance low light low ppm's big light big ppm's. Healthy plant more ppm's sick plant low ppm's. Same goes for roots nice root structure more ppm;s root rot low ppm's. Balance.

70's natureboy said:

All your numbers are fine. The cal mag could be a little high but if you are using half the recommended then I would roll with it. I burn leaves all the time and they don't look like yours. Yours look like they are sick from the nutes or PH but your numbers are ok. That's why cocoa and led's are tricky.

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What do you think I should try to do? Should I lower the nutrient concentration? They started looking like this during the stretch, and I was giving them 500ppm nutrients (170ppm of CalMag).

Bernie420 said:

How many ml to how much water gives you 170 ppm of cal mag?? Seems like alot to me (the 170) but you dont have a calmag problem. Maybe drop that down to 100ppm if that is how you do it.

Does the 170 seem high to anybody ?????

Ok, that is kind of what they look like I dont see a problem myself. But if that was my grow I counted about 14 stretchy colas, I would bend, (supercrop) all of them straight horizontal towards the outer area of the grow where I could and even out that canopy.

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Yes it does seem high, but I would have to measure 5 ml per gallon to know for sure. op, don't forget cal-mag is nitrogen, good luck

Bernie420 said:

My rule I go by is that I dont like to go much past the wattage of light in relation to my ppms

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For your rule of thumb, are you considering the wattage of an LED or a HPS? I imagine a 600W HPS puts off less light than a 600W LED, so your rule probably works best for one and not the other.

Also, is it normal for only the very top leaves to be showing signs of nutrient burn? Only the cola tops are really showing the yellowing tips.

Beachwalker said:

Yes it does seem high, but I would have to measure 5 ml per gallon to know for sure. op, don't forget cal-mag is nitrogen, good luck

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I measured 370ppm when using 5ml per gallon of GH CaliMagic. My meter could be way off, although it is consistent.

Honestly your babes look fine...the new growth is always lighter green, i mean look at your garden its a master piece, leaves are perking up reaching for the light they have beautiful shape and size as well as color. You might be over estimating yourself here, just my opinion. Maybe add more light for real.

beepy1 said:

For your rule of thumb, are you considering the wattage of an LED or a HPS? I imagine a 600W HPS puts off less light than a 600W LED, so your rule probably works best for one and not the other.

Also, is it normal for only the very top leaves to be showing signs of nutrient burn? Only the cola tops are really showing the yellowing tips.

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i use hps so its hps for me I imagine it could work for led idk. 600 watt hps or a 600 watt led seems legit. Was at a guy house last week he was vegging with 600 watt hps and feeding 1350 ppm in hydro, told him he had a problem. They were little plants. Just thought it was a good rule of thumb to pass on.

yes at the top is where you'll see it first.

beepy1 said:

I measured 370ppm when using 5ml per gallon of GH CaliMagic. My meter could be way off, although it is consistent.

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What was you ppm before you add the calmag?

I used botanicare calmag and 5ml in 1 gallon of r/o water with a starting ppm of 10 put me at 150 I added another gallon to that and it put me at 80 = science.

so anyways I think that coco you need to add more of the cal mag or just cal in for some reason if I remember right I just caught that your on the coco but I dont use coco and when I use the calmag I only use 1-2ml per gallon myself for my set-up so maybe the 170 is fine my bad.

Master_Tabi said:

Honestly your babes look fine...the new growth is always lighter green, i mean look at your garden its a master piece, leaves are perking up reaching for the light they have beautiful shape and size as well as color. You might be over estimating yourself here, just my opinion. Maybe add more light for real.

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Master_Tabi said:

You might be over estimating yourself here, just my opinion. Maybe add more light for real.

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Thanks for the advice. Why do you say I'm over estimating myself? Also, are the yellow tips (of the top leaves) a common thing during the stretch? If not, what do you think is causing that?

Over estimating your problem, excuse me. When the plant starts to stretch the new growth has a lighter pigment. You're welcome I'm no pro but I love plants.

They look nice.
Brown tips are not only nutrient burn. That ppm don't sound that high for the size of the plants. That's around 1.0 EC depending on the meter/scale that's used. (500/700)

What's your heat/humidity like?
heat at the canopy?