...identifying this illness on a male yellow lab. Strange red growths on back and fin with an apparent open sore. Activity is normal. Tank conditions show a slight amount of ammonia; all other tests normal. No other fish showing similar signs.
Unfortunately there's no cure. It's brought on by stress and kind of like the fish version of cold sores. You could isolate and treat this fish with antiseptics/antibiotics to prevent secondary infection in the open wound on the fin, but that's about the best you can do. Try to assess what you've been feeding them (is the food older than 6 months old) and consider adding a vitamin supplement like VitaChem or increasing water changes. In an African tank, odds are he's being picked on enough to cause stress.
Sorry I didn't reply to your message; dealing with health issues. Anyway, this used to the tank bully which may have its own stress. Now he shies away from most others. The wound healed but another growth appeared a week or so ago. And now he's slowing down. Feeding is comprised of Cichlid gold pellets, Cobalt flakes (maybe a little old now), lettuce and occasional frozen food.