Are you top feeding or bottom feeding? Idk know if this is a solution for you but when I started bottom feeding rather than top feeding it made a huge difference for me. Seemed to help with ph issues and overwatering issues not completely sure thats your issues. Good luck hope everything works out in your favor. Just do small changes see what helps hinders and move from there.
The these plants are in 1/2 gallon plastic pots. There is good flow through the pot. The run off is a tea color. I top feed as these are in soil. Temps average 72 degrees and humidity is 60%. Lights are led’s, 3500k.
So I mixed up the nutes I have and checked the pH after with my strips, waiting on my pH meter to arrive, and I got a pH of 7.5. The plain water tested 7.0. I added a 1/4 tsp of lemon juice and it dropped to 6.0 for 1 gallon. For the three sickly S90’s I made up a gallon of water with a cal/mag supplement to flush them.
Edit: last night it dawned on me that my led lights are too close, 16” from canopy full intensity. Did some reading and too much led light mimics some nutrient deficiencies. Raised the lights to 30” above canopy, leaving intensity at 100%. Learned something new.
your too cold, your issue is there is not enough heat for proper photosynthesis, not a nutrient deficiency
Where is the temperature sweet spot?
for LED you want 80 degrees and 60% humidity or higher with sick plants… only can run lower humidity if the plants are bumpin… with sick plants 65%, 70% to just limit transpiration and allow the roots some time to develop
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Yeah i second that. Sorry for the late response, OG did not notify me of your reply. Your temps are too low, nitro has you covered. If you were blasting them with intense LED then it really would have had a hard time.
I have increased the temp and raised the light. The plants seem to be responding positively. Now I found I have spider mites and have some lady bugs arriving tomorrow to address the issue. Well if it’s not one thing is another.
Sorry to hear that, you’ve got to lower the temperatures and raise the humidity as much as you can, mites don’t like that and they are the higher menace for your plants at this time … 
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Hahahahh, gotta raise the temps to make the plant happy, gotta lower the temps to get rid of the mites. Your damned if you do, your damned if you dont 
Great that you have lady bugs coming so quickly. Didn’t waste any time.
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So an update, the three plants in question have turned the corner.
Before
After (17 days later)
Now I have unleashed the hounds from hell on the spider mites!
Growing under LEDs has a bit of a learning curve, but not too steep. I have also switched nutes from AN m-g-b to GH maxi-grow and bloom.
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I’m glad I read this today… I grow on the cooler side, 65-70*. I would have bought LEDs and been so confused. Glad you got that sorted.
My temperature varies between 73-75 degrees and the plants are thriving.
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That is a solid turnaround!!
I keep on thinking I’m deficient…I keep my water stable at 6-7ph…the odd time it floats up to 8 
…but thats few and far between. I’m gonna try raising the light and transplanting my ugliest girls into large pots.
Thanks for the good info everyone and Tejas for sharing!!
edit…my flower room temps fluctuate from 29c with lights on and drops to 17c lights off. Veg room stays consistent at around 21c…however humidity usually sits at 30% in both rooms.
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Yeah that humidity is pretty low too. I am not sure if you have anything to help control night time temps but if possible you want to try to limit the temperature difference between night and day to be no more than 10C ideally. You may not be able to control that and it wont be a big problem. Just not ideal.
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So I should probably put my fan on my light timer so it is not running when the light is off??
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Fans are used to strengthen stems and avoid stagnant air that could cause mould, with your low humidity that is not the case, you may do that … 
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Perhaps just keep a small circulating fan running
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