Did you just get him? I had the same problem. I had a tree frog for only 4 days and its skin looked very similar to yours. I found him dead yesterday.. I wanted to take him to the vet but he died. I did everything I could for him but I think he just didn't adjust well to the new habitat. When I brought him back to the pet store they said sometimes if they stay in the store for a long period of time they get sick. I am really sorry for your lose. I couldn't get him to eat either.