yellow tang with brown spots

[HelenMac]

I have a yellow tang that suddenly has large brown spots.
Has whole line of them where top fin joins the body and looks reddish under the skin. Has some on the fins also they are quite raised and some look like there is something hanging off them. I have put him in a isolation tank he is happy swimming round chasing glass shrimps and eating. Still is his normal bright yellow apart from the reddish areas where the spots are under the skin..

Nothing has changed in my tank except for the last 5 weeks been using asw for water changes. All other fish are fine.

What is this and how do I treat it.

 

[BorHor]

My yellow tang had the same problem when a purple tang I had started picking out it out of not where. I isolated the yellow for a week or so and gave the purple to a friend. When I put the yellow back in the display tank he still had the spots all over but I figure I will see if it will take care of it self. Slowly the red started to disappear and took about 2 weeks to be back to a solid yellow.

 

[HelenMac]

There's no one picking on him he is the largest fish in the tank. His tank mates are a baby convict, copperband, yellow tale damsels and a coral beauty.

 

[HelenMac]

managed to take some pictures with flash