The bottom part of the plant don't get as much sunlight or florescent light as the top and will drop them. even more so with more plants n the cage. I get my plants from home depot so anytime I don't like the way the plants are looking I return n get a new one
I had mine together too. one was eating more and taking the basking spot. Was getting bigger too like urs then I put in there own cage n the smaller one is actually bigger one now after a few weeks by alot.I recomend seperating them they do better no stress