Purple tang with large white spot

[Hands_in_pocket]

i have not added any new addition in approx 6 months
pics

he eats well and no other fish are bothering him, he isnt acting unusual in anyway
params
P.H:8.2
Ammonia:0
Nitrite:0
Nitrate:0
any advice is appreciated

 

[shorty53538]

Honestly, its super hard to see anything with the pix....

 

[Hands_in_pocket]

i circled the mark but the spot is almost completely gone now, could he have rubbed up against something and i was just overreacting?

 

[eyebedam]

I had a grouper that would do that when he was upset. I wouldn't last but 15 to 20 mins max but the first few times it happened it freaked me out.

 

[5h3rW1N]

it probably stressed from something