First fish loss

I'm gonna go against the grain here and suggest waiting a month or two. Your clown will develop into a female in the absense of another clown. Then, when you go and get a new clown, pick the smallest one of the bunch. It will eliminate the battles of dominance that happen when 2 males fight over who will be female. That's actually the preferred method of getting paired maroons, but can go either way for Amphiprion breeds. Personally, I prefer doing it the way that will minimize the fighting.
As far as the ich, feed the tank garlic extract soaked foods. It will boost their immune system so they can fight off the infections naturally. Moving to a QT will only stress them out more. Chemical meds only mask the problem and usually result in residual problems, and more times than not, the problem will reoccur very soon.