2 pale areas at dorsal fins in chevron tang - what is it ?

[joaovieira]

My chevron tang is at quarentine tank (4 weeks tomorrow) and is doing great. He is eating a lot mysis and nori. Three days ago i have noticed two pale areas (they are not bumps or ulcers, nor really white, they look like dispigmented areas) of about 1 cm length each, both localized ad dorsal fins (left side). Both areas have not showed any evolution during these three days. I am not sure he didnt have them when i bought it. unfortunately the pale area is so subtle i cannot really picture it.

What do you think is it ?

Thanks everyone :thumbsup: