Don't worry too much about the bottom set of leaves yellowing and falling off, this has happened to almost every plant (cannabis, tomato, sunflower, pinto bean, etc.) I grow whatever the medium. Warped leaves sometimes occur in younger plants just as human babies can look all out of proportion; the problem should right itself in the next set of leaves or so. If it doesn't, then over-watering might be to blame. With over-watering, leaves stay firm but curl downward and will start to warp if not remedied.
All that said, it's just weed. We all get excited for our first grow and want everything to go perfect, but we forget that left alone it will grow just fine (you might even say, "like a weed"). I'm taking a more laissez-faire approach to my plants and they're doing way better than when I obsessed over them.
I also agree with Gutta and PTSD that CFLs should be placed as close as possible without burning the plants. Keeping a small fan blowing over the plants and lights will further help prevent light burn. Here is a graphic to illustrate the inverse square law of light, which is important to keep in mind if you want to get the most from your CFLs.
Love the grow box! Very clean and well constructed. You can count me in on this journey!