Not sure what's wrong with my girls.

Everything was fine until I lowered the lights a little bit.
The two plants in the center getting hit by both lights looked worse to me. I am also getting what looks like rust spots on the leaf. I removed all that I could find.

In a 5ft*5ft with 2x 315 CMH .
Growing in canna Coco with A+B , calmag and a root stimulant. PH around 5.9-6.1

I definitely wasn't over watering them. I up potted three weeks ago, if anything I thought I may have been underwatering
After taking these pictures I raised the lights right up high and fed them with a slightly weaker mix + a dose of O2 hydrogen peroxide additive.

The last two pictures is the cheese that I am most concerned about.
I had planned to switch in a week or two but I really need to get them healthy first . Switching asap is important because it will start to get warm soon!

Any advice appreciated

On the last pics I noticed the lower leaves on the plant didn't seem as bad making me think maybe it was too much light or stress too down

Coco needs to be watered daily to 20% runoff.. You're underwatering..
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Ahah, I have been watering when they don't feel too heavy any more , or top layer of soil is dry.

Watering everyday gave me some fungus gnat problems in the past.
I shall up the watering and lower feed concentration or keep it the same

If underwatering is what's causing this. I'm not sure 20% run off daily is ideal for these size plants in 25ltr of Coco.

Most coco growers use 2 gallon pots so I don't really know about drainage in 25 liter pots..
If you haven't been watering to runoff you will have salts built up in the coco..
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Too much light I see bleach spots

Calcium and mag deficiencies as well from probs bad water practices

Mag deficiency, possibly lacking in iron as well. Have you double checked your pH meter?

Whats your ec at?

I raised the lights and watered the hell out of them with a slightly lighter mix but full calmag and some hydrogen peroxide.
Also raised humidity and they have really perked back up, lush and green!
I don't check EC only PH and that was calibrated perfectly