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That product is an herbal tonic, made from various tree oils. It does not seem to work for most people if their fish have active infections. The trouble is that there is such a strong market for "reef safe" medications, and there is no oversight to the market, that companies take liberties with a few studies out there and make up their own elixirs, and people buy them because they present an easier solution.
The two best marine ich treatments would be copper or hyposalinity. The tank transfer method can also work.
What often happens is that when Cryptocaryon/ich first starts up, the parasites are all more or less in unison, and so when they all drop off to reproduce, it SEEMS like the medication is working. However, then their daughter cells return and infect the fish, and they get spots again. Eventually, they become out of sync and the fish gets more and more spots and eventually dies.
That said, you clown may have other issues at the same time. What are the water quality tests running at?
Jay