Help spots forming on fish.

[Slyguy00]

So my tank is about 6 months old, water perameters are all within specs, I do regular water changes, and basically keep everything as good as it can be. But for some reason I have noticed little white spots starting to form on the fins of my two tangs, and no other fish. I havnt added any fish in a few months and everything was fine this morning. How do I tell if this is ich? And if so how do I take care of this? Any advice would be appreciated. Thanks