Maybe a sick Rosy Barb
I have what is hopefully a non-issue, but maybe someone with expertise can help me out. I've got a school of 5 rosy barbs in a 29G tank. Four of them are fairly typical - having way too much fun with anything they find. But lately the fifth one has taken to sitting in the corner, almost moping. He doesn't get picked on, and he'll come to food, but he's not acting like a barb. Another observation is that his mouth is always open and he has little red spots on his upper lip. Can't tell if those spots are on the others.