Myco starts on the inside of fish. Normally the kidney, and spleen are affected first, then soft tissue. By the time we notice the lseions, it has a big head start. Normally fish will show a small red/ pinkish lesion. the flesh sloughs off a bit, then sometimes looks like its healing. The spot will remain a lighter color than the rest of the fish's body. Sometimes there will be several lesions show up. As it advances, some fish will develop a curve to their spine, and also a portion of the fish will turn black. This is normally in the head area.
As far as I know there is no (cure) once their infected. Kanamycin has helped alleviate some of the symptoms. Affected fish can live quite a while with Myco. Keep the water very pristine, and feed a varied diet to keep theie immune system active. If you add more fish to the tank, be aware there is a chance they will contract it also. But I have had cases where fish were added to a known contaminated tank, and never became ill. That's not to say they didn't have it, but just never showed any symptoms.
Several of us Rainbow breeders did lots of research, and experiments to try and figure out more about this disease. Gunther Sveda the most knowledgeable bow keeper/breeder even helped out with the research.
All that being said, I am not diagnosing your fish via the forum. Just giving you a tool to work with. If bacterial meds clear it up, and keep it away, then obviously it was bacterial. If not the further research is necessary.
