Fin Rot?

[captain hook]

I'm not sure but I think my yellow tang had fin rot about 6 months ago. Both his top and bottom fins looked like they were beginning to thin and then waste away. I pulled him out of the main tank and treated him with penicillin for a week. I'm not sure if this was the best medicine, but it's what I already had at the time. It seemed to work. I put him back in the main tank and his bottom fin began to grow back. Now it's completely back to normal. Unfortunately, the top fin is still eroded. It's much thicker and stronger than before, but it hasn't completely filled in. My question is there something I can do to help the top fin fill in. He looks kinda funny right now. I always just assumed it would eventually grow back, but 6 months later still no signs of growth.

 

[captain hook]

Typically, I feed twice a day. Usually, a flake food once and frozen food once. I usually alternate the frozen between Emerald Entree and Spirulina enriched Brine Shrimp. I also try to add a some Brown or Green Seaweed Select once a week for my two tangs. I have a 75 gal tank with 6 fish in it right now. I have a green chromis (he's lonely), a firefish goby, a pygmy angel, a tomato clown, a hippo tang, and the yellow tang that's in question. The yellow tang is the largest fish in the tank followed by the hippo tang. Does this shed any light on the situation?