dehydration most likely hows your humidity and is he eating? I have 2 balls my self and my oldist did have this issue when he was young. My vet told me it was dehydartion i need to change sub stright and mist my cage more have a bigger water bowl for him to soak in. Great things about balls are is they are sick they snap back fast that was 6 years ago when my guy was sick and hes still here with me