This just a guess but seems to fit with information given.
DROPSY - is a bacterial disease that attacks nearly all the internal organs of the fish, causing a concentration of fuids in body tissues or cavities. This results in a general swelling of the fishs abdomen, thus causing the scales to protrude from its body.
Be careful when making the diagnosis not to confuse dropsy with egg binding.
Treatment for dropsy is virtually the same as for tuberculosis.
Symtoms - The body will have general swelling with protrusions of scales. The eyes may also bulge.
Treatment - Dropsy is not very infectious. However, the treatment for its bacterial cause requries that the fish be treated in a separate hospital tank.
Medicate the hospital tank with a proper Marine antibiotic manufactured for dropsy or gram negative bacterial infections, such as nitrofuran (furan) or kanamycin sulfate (1st choices). Ask your fish dealer to recommend the brand that has been the most successful. (aureomycin, neomycin sulfate, tetracycline, oxytetracycline, or nalidixic acid 2nd choices)