With him dragging his body around like he was (I know how he did it because of Flop), it's no wonder if he has a little case of finrot going on. Flop had it pretty bad there for a while, but he has some really nice fin growth coming in on him now. Just keep his water clean and dosed with some aquarium salt, and it'll heal back in just fine.
As for the other question, could you get a picture to illustrate your point?