I had the same thing happen with my Coral Beauty. I feed my tank a variety of algae, veggies, meaty foods and the fins started looking pretty bad. Looked like fin rot to me. Not your's.........I am talking about mine. Your's doesn't look that bad. I, for three days running, soaked the food in Melafix and garlic and just fed once daily. She rebounded perfectly. Whether it was the melafix or time or it's own immune system, I don't know....but that's what I did.