What's wrong with my cory?

[NuttyMalik]

He's been like this for a couple weeks, he's acting completely normal and happy with the 5 other Cory's that don't seem infected
I don't think it's a fungal thing since I did a treatment for fungus not long ago
His skin has started to peel of abit
Parameters are fine

 

[Autumnsky]

Was there ever an ammonia spike around the time you started seeing it? It is possible the fish is experiencing a resulting infection from that time?