Is My Flounder Sick?

I bought a couple freshwater flounder a couple weeks back. Unfortunately I
put them in a tank with "mildly" aggressive cichlids (they managed to kill
two other cichlids, all of my shrimp and the crawdad). They ate one
flounder and the other is badly scarred on his back with his fins all torn
up. I have traded in all of my cichlids and I am wondering if the flounder
will ever get better. I have treated the tank with Melafix and Fungus
Clear, it has been a week since the cichlids have been removed. The
flounder's condition has not improved. He seems healthy in that he swims
around and acts normally but his fins and scars are not looking good.

Here's the catch: I want to populate my tank with Mpimbwe Frontosa, they
shouldn't be nearly as aggressive as the other fish I had. But I don't want
to introduce them to a tank that is infected. I have had two other fish
that have inhabited this tank through this whole shebang (a bristlenosed
pleco and a flying fox) they are doing superb. They show no signs of
disease. How can I tell if my flounder has a disease? Should I flush him
now before the Mpimbwe arrive in case he is infected? Or should I take a
chance and simply introduce them as normal?

Should I add Fungus Clear when I do introduce just to make sure? What other
precautions should I take?

Thanks,
Muuurgh
--
"He felt that his whole life was some kind of dream and he sometimes
wondered whose it was and whether they were enjoying it." -D. Adams