[First random thought was it was acne on a juvenile fish. :D
But seriously said:
[Yes, I agree completely. Fish cure themselves all the time. You can almost suspect that most diseases are the result of some stresser or other. These parasites, fungi, and diseases are in the water all the time. They aren't usually affected unless their health deteriorates, usually due to shipping stress, some tank parameter sometimes, or another fish that harasses them, or feeding schedules. Who knows really what stresses a fish? A bad fin day, maybe? I don't know. But as the stressers are removed their immune systems get back to normal and it goes away. Ya know, the best you can do is let em have access to a cleaner shrimp and if they're happy they'll do well. I have worse luck actually trying to QT and treat a fish. They always seem to die if you subject them to the stress of moving them. And I loose fish all the time when I keep them in smaller tanks, but in my big tank, I hardly ever loose a fish unless I just can't get him to eat when I first add him to the tank, even that doesn't happen much. The only difference is more stable tank parameters, more places to hide, more fish to play with and coral frags to knock over at my expense. All the things that make them healthier and less stressed basically.]