Guppy - White Mark With Blood In

[Raindancer411]

Hi All

I just had a look at my fish and noticed that on one of the guppys at the base of their top body fin there is what looks like a white mark with blood in the middle. I am wondering if this is either an ulcer or where it may have been attacked by another fish. I cant get a good clear look at it but there doesnt appear to be any fluff/cotton wool to it. Any ideas and how to treat it?

 

[WILDER]

Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

is the fish actling,listless and lethagic.
Is the fish acting diffently to normal.

It could be an injury.
Is it possible to load a pic up onto the site.