Dry and droopy leaves

OK to start off, please don't tell me my plants are over watered, as I am 99% sure this is not the case, but seems to be the most suggested cause of droopy leaves.

The leaves on my plants are very dry and droopy. One of them has been this way since incurring some root damage about a week or so before Christmas, but this is a more recent phenomenon for the others.

I went out of town for about a week over Christmas and came back to find the plants looking great, but pretty droopy/thirsty. I came back and gave them a feeding with GH flora line nutes, their first feeding ever. Well, all but the one with root damage perked up immediately. However, I mixed nutes at full strength, which I quick found out was a nono, especially using high fert soil like I do. They quickly went from being perky to showing nute burn in the leaves and leaf tips the following day. edges were drying and brwning and tips were curling.

I didn't want t re water them right away 36 hrlater so I gave them another 36 hours before flushing the soil. Flushed the soil with CO tap water (live near the mountains so I have always used tap water as it is pretty darn good). I have never let the water stand for 24 hours before using, but plan to from here on out. Now I fed them again a couple days ago with plain tap water, but tried bottom feeding (filled their drip tray with about 3/4 liter each to be absorbed from the bottom), as someone suggested it may be a drainage issue and this could help.

Well, it's been 2-3 days and they are still very droopy. Leaves are VERY dry to the touch and curling down badly. I need help! There is still slight moisture under the top 1/4 inch of soil and by the weight of the pots I can tell it is not too dry yet.

some more details:
-I am growing in a mix of 2 parts roots organic 707, 1 part roots organic green fields (high N soil), and 1 part coco.
- I thought I finally solved the conundrum yesterday when I got a 16% humidity reading. However, using a humidifier and a wet towel, I have managed to have the humidity up to 50-55% for the last 12 hours or so. And no change.
-Temps are 70-75 with lights on and get as low as 60-65 during the 6 hr lights off. I have even seen readings in thehigh 50s
-plants are about 6 weeks from clone cutting
- all are different strains and did not previously exhibit these symptoms (at least not to this extent), so it's not gengenetics
-pics are attached

My current plan of action is to flush the soil they are in to rid of any nute builup that may still be present, transplant them from 1gals to 3 gals, put a fresh layer on top to lower the height above soil and to allow the water to drain through it with some of the nutes in the soil for a light feed and give them a light water. Let them go for a few days and examine further? Any other suggestions? How should I proceed with feeding from here on out?

i also plan to get a ph meter today so I can get readings for that.
 

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Would salt buildup really happen after only one feeding (albeit botched)? Can I flush with tap water or should I use distilled since I can't let the tap water sit? Per the local water report compared to numbers gained through research, it is ok to use for feeding but not sure about flushing.
 
if your soil already had fertilizer in it, then you fed it it can be salt build up. but i think its both root bound and overfed
 
Will it recover from the salt buildup even if its root bound?
If you flush and re pot it should Be fine. Don't fertilize if there's already fert in the soil if you must, make it a very mild solution. i would recommend using a soilless mix without any nuts. it makes feeding easier
 
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