Its a tough one but i think hes just too wet. Try to vary the humidity throughout the day instead of always being around 75-80.(50 to 80 throughout day works for me) I had the exact same problem with my first frog too, but he survived in the end. Trick is not to worry, something i do alot . Also, the changing food around thing might not work for yourself. The reptile shop owner suggested i do that.