IMO. Your soil has looked wet in all pictures, either you take pics after watering, or water a bit too much. FYI that light in the mrgrowpro is adjustable, you can lower it to your plants rather than raise the plant to the hottest part of the box. The seedling that died, I'm just wondering if it got too hot up there. Even if the temp was 85 or lower, a seedling could always use a dome over it, little clear Tupperware bowl works great to trap humidity in while she takes root. And only 2 bulbs above head screwed in for a little girl is all thats needed. She couldn't begin to use all that light at seedling stage, and would prefer not the heat. Just something to remember for next time. Sorry i didn't get here sooner. As for the leaves at the bottom, i wouldn't worry too much, i bet she pulls out of whatever nute burn or deficiency she felt. You're going to need a bigger pot. That included tub fills out the bottom better in my opinion. Whatever you can get the most soil in is best.
Hope that helps