The first 2 pictures are the second white widow to sprout but soon became the larger plant. She's started to show a bit of discoloration and I hope it's just needing a couple nutes. We have a general purpose 20-20-20 I mixed in with the water for the first one. I've given this one nothing but straight water but it was originally planted in soil with a little added phosphorous. It's the only kind I could find without a bunch of other stuff added too. We're still looking around for better soil but for now it's what we have. I think it's lacking nutes but I've never done this before so I don't really know alot about it yet. The 3rd picture is the first plant. They're both 15 days old and until now have looked good and strong under a 100Watt CFL and have stayed between 74 and 82 F.
The light is only a 100 watt CFL. Not the equilivant, it's a huge ass light bulb and I've kept it between 2-4 inches from any plant at any time. It barely puts off enough heat to keep the closet warm. I've raised the light since then and I agree that the damage resembles nute burn but it's the first plant out of 9 that I've used with this soil and I've actually even watered these plants more thoroughly than those in the past despite the poor and decreasing drainage. (Potting mix sucks people). We're probably going to start growing out of our own soiless mixture once we find everything we want but until then I just want a few females to smoke.
the curling of the sides, could be a salt lock it's some kind of an uptake root thing going on there, try fox farm, dont fert it for two weeks, clean water every 2 1/2 3 days to get back on track, then after two weeks hit it with nutes and fert's use half of what the bottle say's at first. you should be looking good then. dr hornsby juice and fish-mix thats a good combo. good luck
I vote overwater, that yellowing, drooping leaf speaks volumes. Also, your soild looks like it is very compressed. Time to get some foxfarms and repot. P.S. that general purpose ferts your using is going to cause you problems so when you order/get your soil get some good nutes as well.