Dwarf angel skin issue

[Tracers]

This is a recent development. My coral beauty angel has the same raw looking area on both sides if the body. It started out looking like another fish had nipped it but it keeps getting bigger He is eating fine and seems to behave the same as always.
I have a 65 gal w a 20 sump the tank parameters are all zero nitrate nitrite and ammonia my ph has been a little off I'm checking it daily to get it back to 8.3.
There are 3 chromis a clown a box fish a long nose hawk and a sailfin tang w my angel. There are a few feather dusters and the Kenya trees
Any help would be appreciated

 

[Plecolover18]

To me it looks like a fish attacked him or he scratched it on a piece of live rock also I'm new to corals but maybe Kenya trees or the other one u had stung him at night when he was asleep as I said I'm new to corals so I don't really know.

 

[Gregcoyote]

Those corals don't sting fish. He may have a parasite he is rubbing against the rocks to eliminate. Flashing can cause some skin irritation. He also may have some injured scales, look closely. They get these fighting or accidentally hitting rocks. Poor water quality can also irritate the skin.

 

[Tracers]

My water quality is good. I haven't witnessed the fish fighting but I suspect my Sailfin Tang might be the problem. I figured it was an injury but wanted to see if it looked like something else to others! I would hate to miss an obvious parasite / infection.

 

[Gregcoyote]

My water quality is good. I haven't witnessed the fish fighting but I suspect my Sailfin Tang might be the problem. I figured it was an injury but wanted to see if it looked like something else to others! I would hate to miss an obvious parasite / infection.

If the sailfin damaged the fish then a infection could be the next thing. Watch the area to see it doesn't redden worse. That reddening is actually bleeding under the skin from irritation or damage. Like a bruise.