Regal tang question

[howdy20012002]

I have a beautiful 6 inch regal tang.
She has always been a recluse but lately I never see her.
She now hides at the back of the tank all the time.
I am getting a bit concerned because it has been about a week since I have seen her eat and normally feeding time is the one time I would definitely see her.
Does anyone know if regal spawn or anything like that?
any input as to what is going on?
I haven't introduced any new fish in a few months and she looks fine when I am able to shine a flashlight on her through the rock.
I just don't want to lose her as she definitely is a beautiful fish
Any input or opinions is, as always, appreciated
thanks in advance.
Neal