ich - blue tang?

[daplatapus]

There's a good read on ich in RC's fish disease and treatment section written by Snorvich. It goes thru the life cycle of this parasite and can give you some good understanding of how to deal with it based on sound logic.
When you no longer see any white spots on your fish may mean your treatment is working OR it could just be the stage where the parasite drops of the fish into the substrate where it multiplies. In a couple days or if/when your fish are stressed, you may see another outbreak. Typically these 2nd or 3rd outbreaks are much worse than the first as the parasites multiply.
Knowledge is definitely our friend here. The sooner we can recognize signs and symptoms, the better we're able to help our fine finned friends.
Garlic soaked foods do appear to really help the fish's immune systems and I feed mine 2-3X a week as well. I've never used the Kordon's ich attack but hopefully it'll help you out.