Is This Fin Rot? Help

Is this fin rot or is another fish doing this to my Cory cat. I know pics are blurry but damage is to top fin and his underbelly is turning white. What can I do to help him?

 

The pictures are blurry and i can't tell specifics, but it definetly looks bad. Could you post a better picture? This looks to be a gram negative bacterial infection, but can't be sure yet. The fish looks pretty emaciated also.

 

Best pics I can get with phone