Emerald Cory with Brown Fin

I got a emerald cory from the fish store a month ago and he looked like a emerald when I bought him, but recently hes gotten brown accents on his back and fins. Is something wrong with him? Or is it possible it is really a bronze cory? His behavior is normal and he is very active, so I don't think he's sick. Just wondering if the color change is normal for emerald cories.

 

Anybody seen this before?

 

A picture would be helpful If he's eating and acting normally I wouldn't worry too much.
Carol

 

sounds fairly normal to me, have you noticed any fraying or signs of fin rot at all?

 

No fraying, just a brown patch on his back fin and tail. He's doing good, so I'm not gonna worry about it. I'll try and get a picture up if I can find a good camera.