Hmmmm, those don't look too good for 4 weeks old....how hot did they get when they got overheated? They should be larger at this point unless you have been pruning them alot. You seem to have quite a lot of roots for your plants being that size.

Could be the heat or could be something wrong with your nutrient numbers. I don't use GH nutes so I can't tell you exactly what the number should be.

Here is a link to a recipe using GH nutes by someone who is among the best at hydro growing imo....hope it helps..

http://boards.cannabis.com/hydroponi...rt-calmag.html

Also click on the link below my sig which is a really good thread detailing different plant problems with good pictures.

Good luck.