Parasite?

[Splitcane]

I posted this in the clownfish forum with no luck. I'm hoping someone here can help. About a week ago I noticed these black spots on both clowns. They seemed to increase over a day or two then leveled off. I gave it a few days and it started to clear up, or at least looked that way..then it was back and has leveled off at what you see in the pic.

I've read it could be stings from corals or an anemone. They had been hosting in a bubbletip for 8 months before this showed up. It was never a problem but I took it out just to be sure. I also recently added some button polyps so I took those out 2 weeks ago in case they were the issue, even though I've never seen the fish near them. It didn't make a difference. The spots are still there and if anything, are slowly getting worse. The fish act fine. They eat fine, swim fine, bite the hell out of my hand if I have to reach into the tank etc. I'm thinking about maybe a freshwater bath. My Sailfin Tang ended up with some sort of black spot parasite about a year ago. A quick freshwater bath and that was the end of that. He's been fine ever since. I'm just hesitant with this because I'm not sure what it is. Any ideas???