Bargain bin troubles

[Taratron]

So I'm at my fave lfs today, and in their bargain bin $1 tank (basically, livebearers and the like that people bring in) I find a bronze cory, one albino bronze, and one brochis speldens. Sweet, thinks I, and I have the clerk bag them all up.

That's when I see that the bronze cories BOTH have no pec fins. Nothing. Barely stumps. The bronze's dorsal is shredded as well. Nothing wrong with the brochis that can be seen.

I still want the cories, so I ask what happened to them. Usual story short, some moron lady bought the cories, tetras, gouramis, the entire mix of fish, and threw a lot of fish in a 2 gallon tank. Yes, a 2 gallon tank that she had for some time, and had fish corpses in the gravel. Needless to say, she brought the fish back after a day or so, half of them dead, and basically gave them all back. Ammonia poisioning, is what I was told.

Poisoning or not, I have the two cories in a QT tank with Melafix. What else can I do to increase their chance of a recovery? Any meds or the like? I plan on 50% water changes daily, and throwing in some duckweed and hornwort in addition to an air stone.