no worries mylar, means "at the moment".
Ehy man i use little rock wool cubes i soak them the night prior in phof aroud 6 a squeez all the water out , and use the but end of my tweezers to make the hole a little larger(all this occures after germanating)i place the tap root facing down and have the seed just down past the top of teh cube
I have a black grow tray from the hardware store it came with peat pellits (i use for outdoors) it also came with a hood . I have replaced the hood with a 10" heigh hood for clones. any way i have a heat pad from the pet shop 30$ and a 2 foot florecent light hanging over top of teh hood. The tray has channels in it for water to sit and the majority of teh rookwool cube is not in the water. I allow for alot of root to show before i move to my room.
I have experienced the same problem as you in my earlier days. I got to jumpy to getem in to the room when they were not ready. When kept under a hood the leaves retain water aswell as the new small roots.
Whats happening to you is that there is not enough root there to support the leaves when put under MH or HPS and the leaves dry out and it wilts and falls over. Trust me i have been there
One thing to alwasys remember the roots supply the leaves if there aint much for roots then the leaves have to support themselves.
One thing i have also tried i put a waterbottle over my plant i drilled a few holes in the side to allow for some air movement. This seemed to work great . I needed to movem in to my room asap and i didnt think there was enough root ther to support the plant

On a bright not she smoked beautiful

. I hope some of this is useful