I noticed my ACF has some sort of injury/sore/bruise on her lip, any idea what this may be? It looks like a bruise to me, I've purchased some maracyn 2 in case it is some kind of infection, but I'm not sure if it's an environmental issue, the other three frogs look perfectly fine.

Can't seem to get the image uploader to work but here's a link:
https://postimg.org/image/kjwe0449j/