This is the third time I have seen this on one of my fish the first time was an e. yellow so I didn't worry about it. This time its on two at the same time Williams blue lips something I was trying to grow out so I don't want them to have any problems. All 3 times it occurs on the fish right side and just behind its fin, I originally thought it might have just been a bite mark the e. yellow did heal up and is doing fine. The first Williams blue to come down with it was noticed 6 days ago and has been acting sluggish and hides more, but was the first one out to eat today... The second one was noticed today and was swimming fine and ate fine it might be a little more hidden today then the others but not much.. The photo is of the one that was newly noticed today the other one looked identical and appeared to be healing some..

I have the proper salt levels and I do 30% water change 2-3 times a week...