sounds like ick, Is it small white dots? like salt sorta?
If so I would try using some Maracide. Or if not avail try Quick Cure.
If poss. raise your water temp a bit and treat with either of the above.
Ick will live dormant in the tank even after signs are gone so even if it appears to be gone treat the tank with a FULL dose. If Maracide is used treat for 5 days.Ick can affect the gills and eyes along with the mucus membrane. If left untreated it can eventualy kill a fish.
Hope this helps, sorry about short reply. Kinda late and my fins are beat.
Danny