What could be with this plant

Hello Everyone,

I am new to this site and this is my first grow. I did a search for the issues I am having and there were so many different opinions I thought I would post pictures of my plant. I apologize if this has been answered a million times.

Currently growing 3 different strains all from seed. Ninja Fruit, White Widow and Candy Glue. Growing in coco using GH Floraseries drain to waste expert feeding chart. I had issues in the begining with heat stress but have since corrected the heat issues. Currently using 2 600 watt LED and will be using 1800 watt HPS for flower (3 600 watt ballast).

Yesterday, I noticed that my timer did not shutoff when it was suppose to. So instead of my plants getting 18/6 photoperiod they were getting 24 hours of light. I believe this happened on Thursday when I switched over to LED from MH. During this period the plants all seemed to look good. Before this I was dealing with what appeared to be a nitrogen deficiency in 1 of the candy glue plants (Fed plant Floranova Grow).After correcting the issue last night with the timer I woke up this morning with all the plants drooping, wilting and the candy glue that looked to have the nitrogen deficiency looked the worse.

The coco I'm growing in is from rehydrated blocks that I mixed perlite with. It seems to hold water very well in fact in still looked moist today. I typically only need to water my plants every 3 days. After seeing the plants this morning they got fed and all seem to be doing much better however the candy glue still does not look 100% and I'm concerned that all my plants seem to have deep purple stems.

Being that the coco still looked moist ( coco feels cool to the touch but not really moist) could this be an issue with roots not draining good enough? The pots weren't heavy I would say that they were on the lighter side. I water until I get runoff

Could it be stress from the light schedule being mixed up and me correcting it back to 18/6?

Also I do use RO water. I store my RO water in a 35 gallon reservoir. I do not mix my nutes in this reservoir, this reservoir is only for RO water. I take a gallon of RO and mix my nutes in separate jug.

Should I have an airstone in my RO reservoir to provide oxygen? Currently its sealed with a lid and doesnt receive much light. Could my RO water be the issue? I do check my PH and I run between 5.7-5.9 and my ppm of RO is 4 ppm and after adding nutes my ppm is under the recommend amount on the feed chart for GH.

Any help or guidance would be great thanks everyone!

 

Here are some photos of the candy glue in normal light. They look a lot better than what they did first thing this morning.

I tested the water runoff that accumulated in the tray. It had a 790 ppm with a ph 6.6. When I fed them earlier today I had the ph at 5.7-5.8 with 454 ppm. Is this normal to see when growing in coco? Is the ph to high?

 

Here is a couple of pictures of the white widow strain, it looks like some discoloration is appearing on the leaves.