I just got the same problem myself here. Ick outbreak after introducing new fish without QT ( i know very DUMB from my part) from now I will QT everything. Do NOT wait like I did, hoping It was gonna go away on its own.... Very bad idea, after a week or so my fish were dropping like flies. I treated my tank with herbatana, i think it worked somehow but my fish kept on dying. I have a big tank, 240gals. As you can see not a easy job to tear down the tank to get all the fish out for treating. I read some people were having really good results with UV sterilizers. I had one rated for 500 gals, i just bought a new bulb to be for effective. I've been running the UV for something like a week now and the remaining fish look ok. I can say ick is retreating somehow.
I know it could come back with a vengence. If that happens i would have to other choice but to tear down the tank to get them out and treat them with hyposalinity. Oh and i have been feeding lots of garlic (fresh). That has definitely helped. Fingers CROSSED.