Red Around Tang's Mouth

I have an Indian Gold Ring Bristletooth Tang. The past couple days I've noticed sometimes he has a deep red around his mouth/beak, and other times he doesn't. He is very active, eating fine, etc. What could this be? I tried Google and couldn't really find anything.

It is less noticeable during the morning/afternoon, and a deeper red in the evening.

Water parameters:

pH: 8.4
Ammonia: 0
Nitrate: 0
Nitrite: 0

Last water change: 2 days ago

Thank you!!

 

could this be part of its coloration when it grows up?

or a camouflage tecnique?

 

I would search the tank for small tubes of lipstick and perhaps cherry flavored lollipops...

 

I don't think so...definitely not adult color.

LOL I thought he may have been trying out my lipstick, but I couldn't find the tube in the tank. Plus, he could use some application tips. He is missing his lips by a bit.

 

I dont think its a coloration thing for that tang... The adult colors are greenish I thought. The only thing I could think of is some kind of skin irritation the fish may have.

 

The only thing I could find on Google was low pH, and I don't have that. So I don't know what is going on.

 

I did a quick google and came up with either low ph (mentioned) or bacteria. If its not there in the am and shows up later in the pm though maybe its mouth is irritated after grazing on the rock all day?

 

That is an idea. I did see that on Google, but I wasn't sure if that's plausible...since he is built to graze! But could be. Thanks!

 

No opposable thumbs. Also, he probably would benefit from a mirror in the tank...

 

Bindi?

Jack