I had to remove Elton, my Green Treefrog, into a separate container. His colour has darkened to deep brown, and he has become lethargic. I placed him in a container with paper towel, one tree limb and two hanging plants. He has not moved from where he hopped off my hand and landed on a leaf. Physically, besides being thin, I cannot see anything physically wrong with him. Does anyone have any suggestions of what I can do/try to help him?