My Chrysurus angel started this mottling pattern three days ago. It started around his head and has slowly covered his body. Initially, I thought that he was changing to adult coloration. He is eating well (mysis, brine shrimp, Nori, and several kinds of angel food). He is active and breathing normally. There is no shaking or shimming or spots. The other fish in the tank, four butterflies, show no symptoms and are acting normally. He is in a 125 FOWLR with no inverts. No new fish have been added in two months. This really has me perplexed.