As above, could be parasites. It's best give a vet some feces so to get it checked. I have found even the normal ones will get in contact with specialists then proscribe treatment. Quarantine the animal and put it on moist paper towels and clean regularly through treatment, using reptile/amphibian safe disinfectent. Be sure to provide a basking spot of 85F. Just noticed your comment... probably best to treat both frogs.