Can you get a picture of it? What are your water parameters (Amm, nitrite, nitrate)?
Also, try adding some aquarium salt to the water. Actually take some water from the tank, and disolve the salt into that. You want it to be about 1tsp per gal of water. Add the disolved salt water back to the tank a bit at a time over the next hour or so, so it's not a shock to the fish. And turn the heat up a bit. A degree or so at a time until it's around 86 degrees.
It sounds like your fish might have a parsitic infection of some kind, but it's hard to say for sure without seeing it. Ich treatment would probably help with other parasite problems, but it's better if we can get a picture and make sure that's what the problem is before you start treating for ich.