2 Week Old DWC Plant showing some Leaf Discoloration

Hi everybody,

So I finally started my first grow, after lots of research around the web (and this forum especially, you guys are great). My babies are about 2 weeks old, in a closet-DWC. Unfortunately, one of my ladies (I hope) is starting to develop some discoloration on her leaves. It started as what looked like nute-burn after I foliar-fed her some 1/2-strength solution, but then progressed to other spots and other leaves within a day or two. Now the new growth appears to have the beginnings of the same problem.

Some info:
She's in a 5-gallon bucket with some half-strength FoxFarm Grow Big solution, since she is reasonably young still. I don't have a TDS meter yet, as this is my first grow, so I don't know that.
The pH has been right around 5.5, and the closet is kept around 82*F, and since I rent and can't mangle the closet for ventilation, I try to keep the door open when I am home, and keep a box-fan constantly either directly on the plants or helping blowing some air under the door (not ideal, I know, I need an oscillating fan soon too).
The plants are on a 24-hour cycle, and I have backed off on foliar feeding since this problem began. Lights about 4" from plant top.
I'm using a ~250W HO T5 setup (http://www.discountgreenthumb.com/index.php?route=product/product&product_id=3288)
I was using frozen bottles in the res to keep the temp down, but I freaked myself out when I accidentally snapped the tip of a little root by brushing it with the bottle, so I'm devising alternate means now...
Can't think of anything else, but please let me know if any other info would help diagnose! Check out the pics, too!

I currently have an alternate res sitting out with some tap water in it, so tomorrow I will probably swap it out. I'm considering letting it have at some plain water for a day or two, or possibly just measuring a new nute soup. I don't really know how to help her, and I feel like a bad parent... help! I want my White Widow baby to grow up healthy and happy.

Thats weird, never seen that before. Maybe its some sort of plant disease or the brown spots are where an insect has sucked the juices out of the leaves. Have you spotted any bugs??

Negative, I have been keeping a pretty close eye on the plants, too, and have some pretty good all-natural insecticide. The spots where it looks really bright yellow might be from nute burn from the foliar feed, but the spreading yellow from the core of the leaves is what is really concerning me. :-\

Hmmm.

Have a look at this page then and see which picture matches your condition most: http://www.icmag.com/ic/showthread.php?t=11688

I cant be sure by looking at your pics, maybe your PH is starting to go a bit off which is causing a nutrient lockout??

It also looks like your plant leaves are cupping downwards a bit, this could be due to high heat.

So

I put the plant into a plain-water res for a few days, moved the light back a little further from the plants, and improved ventilation. The new growth is looking better, though the old leaves look just awful. The plant is growing even faster than before, and looking pretty good. Some of the leaves are still curling a bit, but I can't really get the heat much below 80F in there, so I'm going to stick it out and hope for the best.

Oh, and blake, the pH has been keeping pretty steady around 5.75 now.

My main challenge now is keeping the res cool. I've been using water-based ice packs a few times a day but I still fear root rot. My roots are slightly browned, and I'm hoping it's just staining from the nute-mix. Is that possible? I'll get a pic of that up shortly.
Bought some Hygrozyme, and added that with a fresh mix of nutes, and the growth is taking off. Excited.

Here are some pics. More soon!

So that discoloration kept coming back (some of the old leaves are so brown and crispy...), but I finally decided with some confidence that it was probably a Calcium def. Bought some cal additive, and things are looking great. Plant looks happier than ever. I'll get some pics up here maybe later today. I think it's time to start a journal, too.

Here are the most recent pics, nice lush green canopy, really spreading out.... looks happy.
I've also included some close-ups of the leaves that were hit hardest by this (calcium def, it seems). It got really far, yuck.
Oh, and look, no more cupping down!

its looking good looks like it recovered, what strain is it?

White Widow. Or, at least, I hope so. I don't know how reliable the source was, but here's hoping! Herb is herb, imo.