Thanks to all that have posted here so far. I am down to my last 3 tropheus now. The remaining 3 however, appear surprisingly healthy and are begging for food at the glass as they used to. I think I've learned a few lessons this time around, and I certainly appreciate the advice I've received here.
I lost about half of the fish while attempting to treat lethargic individuals in a hospital tank. Eventually with so many losses I ended up treating the entire 75 gal. I continued to lose fish, about 1 per day, until 2 days ago.
While I'm stocked up on metro now, it may be some time before I get up the nerve to gamble on another colony. Though something about these fish just keeps me coming back for more. If and when I do, I'm doing a bare-bottom, single-species tank, and I really like the preventative food-dosing idea as well. I tried this strategy, but only after the fish were sick and the sick ones didn't eat any of it!