need help

I can't figure out why my babies are drying up and dying. 2 week old,thc bomb,ppm371,dwc, room temp 78, had light 3 inches away, just moved it up to 6 inches, wasn't sure if I was over heating them. Fluorescent light. Please help!

the more I read I'm thinking it might be heat stress???

here is different a baby same strain. roots not growing, looks as if it's drying up?

Looks like a little nute burn to,

Tend to think a little nute burn too, what's the ppm of you nutes?

Is the water touching the rock wool? Is the rock wool wet all the time?

No, the rockwool is not sitting in the water I have a layer of hydroton between them, but the water bubbles are popping up on the rocks, the rockwool is most all the time.

I woke up this morning to check my plants out and the single root that was dipping into the water of one of my plants, was not there, I guess it fell off over night? WTF?

Ppm is 379