Magnesium Problem Worsening

somedude584 · Sep 2, 2017

Gave them a big dose of Fulvex (1% Mg basically) (5tbsp of per 2gal) as they were showing signs of Mg deficiency. I frequently water with Earth Juice Cal Mag (3% N, 3% Cal 1% Mg) so I'm not sure why I'm even having Mg problems, the soil is amended with about 2tbsp of lime per gallon of soil and the pH sits between 6.5-7.0.

Problem just got worse and spread to the uppermost leaves, they're close to starting flower so I need to turn them around but seeing as the problem got worse I'm not sure what to do. Flushing always seems to cause more problems then it solves, and this grow is 100% organic.

Any advice other than "flush"? Lay back on the Mg? Not an Mg problem?

Here's some high res photos of the problem / full plant view.

SouthCross · Sep 2, 2017

It makes you wonder if that one plant has a genetic predisposition to grow funky. The other plants look strong and vibrant. Picky plant.

I'm at a loss to what the issue is. As you describe it, everything is dialed in.

somedude584 · Sep 2, 2017

SouthCross said:
It makes you wonder if that one plant has a genetic predisposition to grow funky. The other plants look strong and vibrant. Picky plant.

I'm at a loss to what the issue is. As you describe it, everything is dialed in.

Pictures are actually of a few plants, that one that looks a bit funky is the worst affected but the first two pics are of the same plant.

Xs121 · Sep 2, 2017

IMO, I dont think you have a magnesium deficiency though mg deficiency would also show interveinal chlorosis. The other element that would show the same symptom is Potassium deficiency. K deficiency would often show in the lower and middle leaves. If it's my plants, i'll boost the potassium or check if there's any possibility that K have been lookout. Too much calcium and magnesium could actually lockout K.

Did you you have a sudden change in temperature lately?

somedude584 · Sep 2, 2017

Xs121 said:
IMO, I dont think you have a magnesium deficiency though mg deficiency would also show interveinal chlorosis. The other element that would show the same symptom is Potassium deficiency. K deficiency would often show in the lower and middle leaves. If it's my plants, i'll boost the potassium or check if there's any possibility that K have been lookout. Too much calcium and magnesium could actually lockout K.

Did you you have a sudden change in temperature lately?

No, temperature remains stable between 74-81 24/7 and humidity 50-70%.

I hadn't thought that it may be potassium but perhaps you may be right.

somedude584 · Sep 2, 2017

Any other opinions?

Buba Blend · Sep 3, 2017

somedude584 said:
Any other opinions?

If it is a Mg deficiency and they were my plants, what I would do is give it a small dose of Epsom salt dissolved in water that you water with and I would foliar spray the fan leaves avoiding overspray if there are small buds around. The amount I would use would probably vary from what others use, I'd probably use about 100-150ppm's, not sure what that is in tsp per gallon.

Xs121 · Sep 3, 2017

somedude584 said:
No, temperature remains stable between 74-81 24/7 and humidity 50-70%.

IMO, your temp has a wide swing. My temp ranges from 75-77, its rare that it would go up to 78. Having said that, your temp is not bad if everything is dialed in, however, if my suspicion is right that you have a K deficiency or K lockout then your plant would be susceptible to big swing in temp. The bigger the temp difference, the symptom would be more pronounced.

I feed my plants according to what they need (what the're telling me according to my interpretation). What I meant by this, if I dont see signs of deficiency (its better to watch for deficiency than to deal with toxicity) , I just simply feed them with water and from time to time, I would see this.....

note the leaf margin is starting to turn brown. It usually start with some discoloration in the margins of the most mature leaves. I would notice this in one or two of the most mature leaves.

I dont wait for it to get worst, I simply feed it with high Potassium fertilizer then monitor those leaves. In a couple of days, those margins will turn brown, just like with tip burns, it cannot be reverted. However, it stop from spreading to other leaves.

somedude584 · Sep 3, 2017

Xs121 said:
IMO, your temp has a wide swing. My temp ranges from 75-77, its rare that it would go up to 78. Having said that, your temp is not bad if everything is dialed in, however, if my suspicion is right that you have a K deficiency or K lockout then your plant would be susceptible to big swing in temp. The bigger the temp difference, the symptom would be more pronounced.

I feed my plants according to what they need (what the're telling me according to my interpretation). What I meant by this, if I dont see signs of deficiency (its better to watch for deficiency than to deal with toxicity) , I just simply feed them with water and from time to time, I would see this.....

note the leaf margin is starting to turn brown. It usually start with some discoloration in the margins of the most mature leaves. I would notice this in one or two of the most mature leaves.

I dont wait for it to get worst, I simply feed it with high Potassium fertilizer then monitor those leaves. In a couple of days, those margins will turn brown, just like with tip burns, it cannot be reverted. However, it stop from spreading to other leaves.

I think you're mistaken on your temperature swing theory. 7 degrees difference between night and day is actually quite low. We're talking about plants here, that for as long as they have been around have gone through temperature differences on an average night of 10-15 degrees. Not trying to diss you, I just think that you're mistaken in regards to that point.

I have yet to see any necrosis at the tips but perhaps that may change. The curling inward I'm observing could be a sign of a few things, but moisture isn't one of them so that may further suggest it's a K issue. I'm going to try adding some K upon this feeding and will report back. Thanks for your advice!

jbcCT · Sep 3, 2017

Hey bud. I would stop throwing nutrients at your plant. How often are you watering? If those plants are wet, let them dry. I just fed my outdoor for they first time in 11 days.

Maybe, maybe a low PPK organic fert with microbes and dry em the hell out.

jbcCT · Sep 3, 2017

Ya know, I'm of the belief that 99% of problems with cannabis plants are not the plants fault, but us the growers. I try to just leave my plants alone, only responding when the plant asks for it. I take my mistakes and try to learn, the less I intervene the better.

Xs121 · Sep 3, 2017

somedude584 said:
7 degrees difference between night and day is actually quite low. We're talking about plants here, that for as long as they have been around have gone through temperature differences on an average night of 10-15 degrees.

I'm not saying it's a bad thing and you're right about MJ tolerance to temp variance. Heck, people even grow them in the 90's. What I'm saying is temp is not the cause of your problem BUT if you have a potassium deficiency, its symptom is more pronounced when you have a wider difference in your temp..

I even see it at my temp of 75-78 but as not as pronounced as yours (see pic above).

Buba Blend · Sep 3, 2017

jbcCT said:
Hey bud. I would stop throwing nutrients at your plant. How often are you watering? If those plants are wet, let them dry. I just fed my outdoor for they first time in 11 days.

Maybe, maybe a low PPK organic fert with microbes and dry em the hell out.

jbcCT said:
Ya know, I'm of the belief that 99% of problems with cannabis plants are not the plants fault, but us the growers. I try to just leave my plants alone, only responding when the plant asks for it. I take my mistakes and try to learn, the less I intervene the better.

I agree with you. Took another look at the pics and I'm seeing the likely K deficiency. There is probably plenty of K in the soil. It probably is not being taken up by an imbalance of cal/mag ratios or from to much N. Likely to much Mg was added.

BobCajun · Sep 3, 2017

That's just from bright light. Happens to my plants all the time. Mag def shows on old leaves first, not the top ones. If anything it would be low iron, that's what makes tops yellow. but I don't even think it's that, just bright light. You worry too much, that's all. People think every little thing is a deficiency of some sort. Healthy looking plants actually. Now stop trying to fix what ain't broke, before you really cause some problems.

OldMedUser · Sep 3, 2017

Bob got it right. Your plants are growing rapidly and the centers take a while to green up. Mg hit's the old fans first and I'm not seeing any of that.

Treating your plants before a proper diagnosis is a good way to really screw things up.

Nothing to see here folks. Just go on home.

Rasta Roy · Sep 3, 2017

Langbeinite mixed in your soil will solve your issue. It will cover your mag and potash def.

OldMedUser · Sep 3, 2017

Haven't you read the news. There is no deficiencies.

Xs121 · Sep 4, 2017

BobCajun said:
That's just from bright light

OldMedUser said:
Haven't you read the news. There is no deficiencies.

I respectfully disagree with both of you. Blow up the pic and take a look at some of the mature leaves in the shade if its just some lighting effect.

I would rather agree with the OP prognosis with this...

somedude584 said:
Problem just got worse and spread to the uppermost leaves

I think the OP knows what he/she is talking about before making that statement.

Buba Blend · Sep 4, 2017

OldMedUser said:
Bob got it right. Your plants are growing rapidly and the centers take a while to green up. Mg hit's the old fans first and I'm not seeing any of that.

Treating your plants before a proper diagnosis is a good way to really screw things up.

Nothing to see here folks. Just go on home.

OldMedUser said:
Haven't you read the news. There is no deficiencies.

So that we are looking at the same things. This is his 3rd picture.
This is not a deficiency pictured here? This is from light?

Rasta Roy · Sep 4, 2017

Buba Blend said:
So that we are looking at the same things. This is his 3rd picture.
This is not a deficiency pictured here? This is from light?

I'm gonna stand by you needing a touch of Langbeinite in your soil.

Magnesium Problem Worsening

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