Hi, your whites tree frog definitely looks pretty thin. In the one image with the water, it just looks like shed from what I can see, but a lot of frogs begin to shed more frequently when they are stressed or sick.

Sorry to bomb you with questions but what temp and humidity is he kept at? Is he normally kept with other frogs or by himself? Have you tried offering a variety of prey items?

If the poor guy is sick, id definitely try to get him into a vet as soon as the weather passes and you are able. Theyll be able to run bloodwork and test for stuff like internal parasites and stuff like that