I am breeding dubia roaches in a bin. I was told to not use any substrate, as it just makes grabbing the nymphs harder and etc. However, I am seeing a lot of dead nymphs. They have lots of gel water and food, so thats not a problem, and lots of egg crates, and warmpth, etc. I'm wondering, are they falling onto their back and not able to turn right-side up? How do I prevent this? Or is there another reason I may be having nymph die-off? The colony is healthy other than... maybe 1/8th of the nymphs dying. Or is that normal?