I have had two hissing cockroaches die within the last two days. I am brand new to hissing roaches and am not sure what I am doing wrong. These are a part of my classroom science curriculum but I am planning on keeping them as classroom pets. I have the males and females in separate aquariums. They have the proper dirt, and heat lamps, and enclosures. I feed them apples, carrots, bread, leafy greens, celery, etc. I also water them with cubes or gel. The two that passed away did not seem to have anything physically wrong with them that I would see. Any ideas??