lets try not to stir up an argument, but this is what I would do I was in your situation...Research the facts about ich and its lifecycle first and foremost...Second, there are many different pros and cons against products that treat ich. You mentioned that you have a FOWLR tank, so that eases the process a bit, in comparison if you had a reef tank, because most meds arent reef safe. People have many different opinions and experiences when it comes to treating ich. Perhaps dynamictank had positive results with that kick ich stuff, and maybe marrone did not...thats just how it is. Everyone's tanks and parameters are different and there are many things you can do to treat the ich, and the majority of people choose hyposalinity over copper treatment.
Another effective thing you can do is while treating your ich, add garlic extract to the food you feed your fish. I will give you my experience and thoughts on this. (Also a good thing to know, Garlic WILL NOT cure the ich in your tank, it just boosts your fish's immune system to the point that it can fight disease)
I soaked mysis shrimp in Kent's garlic extreme, and let it sit for a while. I then just dump the garlic soaked mysis, and the fish enjoy it alot. Plus, after your ich will be cured, continue to do this to keep boosting the fish's immune systems for the long run.
Another thing that I would say is that I would question the LFS, because the fish that
started the whole mess had to get the ich parasite from another tank. Its not like you get a healthy fish and put it in a healthy well established tank, and suddenly it gets ich.....The fish has to already be sick and have the parasite on it for something like that to happen.
Anyways, best of luck to you and your curing process, and I hoped a helped a bit.