Do I remedicate?

I appreciate the replies to my earlier post regarding the sick redbelly. (Dropsy according to the replies) By the next day he was dead and all I found of him was his head. I went to the LFS for help and couldn't find anyone who knew anything. I got some antibacterial treatment and treated on Saturday. The active ingredients are formalin and benzulkonium chloride. I turned off the filter so the charcol doesn't neutralize the medicine and I am just running the power heads on the undergravel filter. Do I remedicate at some point or do I trust one treament? Do I go ahead and turn on the filter now and repeat the whole thing in a week? The other three fish do not appear ill at this point. Thanks for the help.