Need way more info, but I'd guess Brooklynella. How long have you had the fish? Did you QT? Is it scratching? Is it eating? Is it lethargic? Read the sticky about posting here so we can help you more efficiently.
Yeah, whenever I hear "slime coat" and "clownfish", I assume brooklynella. The pic really looks like brook to me; but pics are always "iffy". This is a very deadly and contagious parasite, it also kills very quickly. In addition to the stickys, Google "marine brooklynella" and you should be able to tell.
Is skin peeling or sloughing off? Is this a new fish, or when was the last fish introduced? IF this is brook, it may be too late to save this fish; but all of the fish in this tank will need to be treated with Formalin and the tank left fishless for 6+ weeks. 9 weeks would be better, ich can be secondary with new fish & brook and ich has the potential for a longer life cycle.