Brown knife fish with ich? Help?

So I bought two pink kissing gouramis a couple weeks ago, and I didn't know one of them had ich until about a week after I had it. The ich spread to the two brown knife fish that were already in my tank, and to the other gourami. The gourami that had it originally died yesterday, though I've put medications in the tank (yes, I followed directions correctly). I just found out today that I'm lucky my knifes are still alive, as they don't handle medication well. I also have two snails (which I took out for to medication), two senegal bichirs, a red tiger barb, a striped tiger barb (the pet store didn't have anything on the label except for "tiger barb," so I just call it that), a striped raphael catfish, and a pleco, all in my 20 gallon. (It may seem overcrowded, but they each do their own thing except for the barbs, and sometimes the bichirs and knifes). Only the gourami and the knifes are showing signs of ich; the others may have it but I'm not sure. Help??