Kole tang turning two toned?

[FrostbiteDR]

Hi we have a yellow eyed kole tang and have had her for 2 months
She is quite happy and eats well and haven't noticed anything unusual with her behavior.
Came home today and noticed she is paler at the front half and darker at the back
Does anyone know what this could mean? Do we need to quarantine her? She's my favourite fish I love her to bits so want to make sure she is okay

Tank specs
Aqua one 275
2x common clowns
5x blue chromis
1x yellow wrasse
1x sand shifting star
3x red hermits
Some snails
Mushroom
Frogspawn
Poylps
Bubble tip Anemone

 

[lt3058]

My Kole Tang used to do this all the time then randomly harass the closest fish. Not sure why she ever did it but she stopped doing it after a few months.