Is this some kind of disease on my dottyback??

[superfish]

They have been in QT for 6 weeks since I bought them.
When water condition go bad they have some kind of bleached color marking on body. ( see picture)
After large water change/cleaning for the QT. the marking will disappear.
But comes back after a few weeks.

I'm not sure if it's some kind of disease??? Although I have quarantined them for 6 weeks. Still don't feel comfortable put them in tank.

Hope someone can help???!!!

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[superfish]

Better pic?

View attachment 15010

 

[vasilithegreek]

I can't tell from the pic, but if the spots look blotchy it could be from stress. If the spots are blotchy white are they on the outside of skin? If so could be a fungus. large Fluctuations in salinity,temp etc....can cause stress and have a possibility of color discoloration at times.

 

[madjoe]

Ammonia burns ?