Whats wrong with my swordtail?

[guppymonkey]

One of my swordtails decided to have a sex change from a female to a male and ever since then she/he has has a spot on the top of her. At first I thought it was a fungus but I am not sure anymore. It is an area about a quarter of an inch long and half that wide where there seems to be no scales. How could this happen? Is she fighting with the other male when I am not around? They do seem to chase each other sometimes. She/he swims fine. Its not growing larger or getting slimy or anything. It confuses me.

 

[bigfish]

What colour is the spot? i have a female platy that has a large black spot behind her gills looks like a birth mark and only stretches when she's pregnant.

 

[guppymonkey]

Its a big white mark. Thats why I thought it was a fungus at first but its not growing or slimy or anything.