What is this colorless spot? PICS

[mattmathis]

I got 2 bosemani rainbows yesterday, and they both looked beautiful. This morning one of them has this colorless place on his side. Any ideas of what it could be?

Thanks!!!

Tank:

70 - Gallon
20 - Nitrates
0 - ammonia
7.4 - ph

Tank mates:

tetras, red-tailed shark, dojos, corys, and pleco.

 

[JustOneMore20]

Possibly some type of bacterial infection. The best thing to do IMO is to QT the fish and buy some anti-bacterial foods.