Bases Of Fins Red

I noticed, a fortnight ago when up close to the fishtank and examining the fish one by one, that a harlequin's pectoral and pelvic fin bases (the parts which join to the body) were actually red. Assuming it's the same fish, it looks the same now as it did a fortnight ago - not swollen but simply red (argh - '80s band not meant to spring to mind here) although he may have been involved in a scuffle as he now has a slight white mark on his mouth  too as though he's injured it and dislodged a scale. Behaviour and eagerness for food is absolutely normal. Water quality is consistently 0 for ammonia and nitrite, and 20-25ppm for nitrate (pre- water change).

Presumably it's just a matter of "keep an eye on the situation"?

I had a had a harlequin jump into my filter, came out with no fins, mouth damage and a scrape on its side - can't tell it apart from the others now except for the same scale on mouth thing so this might not fix itself but otherwise I just wanted to say how hardy a fish I have found them to be.