This is one of those diseases that responds well to good immune-boosting practices. Maitain good water quality, keeping nitrates and phosphates low, and, of course, zero ammonia and nitrites as well as a steady 8.2PH. Use a high grade sea salt mix that says it adds essential marine minerals [read the label]. Add a lot of variety to your fishes' diet, using quality food that has high protein and less addititives and preservatives [again, read the label]. I usually feed my fish 5-7 different things a day ranging from veggies to proteins [greenstuff to red meats
. Preparing variety packed meal(s) for the fish takes a bit more time than just dumping a pinch of flakes or a cube of frozen food, but it is worth the 5-10 minutes of your time. Your fish will love you for it, and they will reward you with better health and appearance. Add to your fish food a vitimin supplement and, also, look for foods that have vitimins added to it [like vitimin c]. You can also add vitimin supplements weekly to your tank. Angels are grazing fish and need vegetables in their diet. You can meet both the needs for grazing and veggies by placing a leaf of rommanie lettuce in the tank if not daily, then every other day. If the lettuce is not organically grown, then plez rinse it with cool water to get the pesticide and fertilizers used by the farmers off the leaf. Do not let uneaten lettuce rot in your tank. Remove uneaten leaf after it has been in the tank for no more than 6 hrs. Also, if your vegetarian fish are not used to lettuce in the tank, give them a few days...believe me, once they get the hang of it, they will look forward to it! Also, add a broad-spectrum antibotic to your tank. This disease is catchy so you need to treat your tank. Don't add any more fish to your tank, especially angels, as they could fall victim to the disease too. Good luck!