Yup brook would make sense.
Scroll down and you see the other guys fish seem (clowns) to have died to what he described as brook and his Mandarin was bubbly.
The reason for the odd appearance is probably their slime coat. I have seen people post similar issues on nano reef and such.
I wouldn't let those fish near my DT until the Mandarin is cured. You could add FW black mollies once you think you have treated everything to try and test the waters so to speak.
Other newer methods are hydrogen peroxide dips which show good promise.
Hello, This is my 2nd mandarin goby that has these bumps on it. At close inspection it seems like bubbles under it's skin. Towards the tail and face there is colorless tissue, like epidermis, peeling off. The last one I had had these bubbles, and I may have killed him with all the various...
www.reef2reef.com