powder brown coloring?

[jreefier]

The next day after adding a yellow tang to my tank my powder browns coloring changed and got somewhat splotchy. The YT got through my partition over night so I didn't witness their first hours together, but have only seen minor swats a few times in three days since they were introduced. Both these fish have been with me for a while and qt'd a while ago so its not ich or velvet or anything like that as its the actual skin pigmentation and nothing externally attached. It looks like just a grainy photo but there are these areas of lighter pigmentation. The pbt and yellow are getting along great now and there's been no nasty attacks that I've seen. It's eating wonderfully and swimming/acting no differently than before. Wondering what in the world this might be? Did the YT maybe scratch it up when I didn't see?

 

[hyeclass]

my powder brown was killed by powder blue. so much space to swim and they killing each other, like humans do

 

[PilotOfSubmarines]

saw similar coloration on my Blonde Naso. I think it has to be some type of stress marking. It was there for weeks and slowly, slowly started to dissipate. He was eating/swimming/acting normal in every way.

 

[Fishnut]

Stressed out. Hopefully they will get along and powder brown will color back up. Same thing happens when water quality gets bad.