Looks like ich to me.My hippo tang used to get ich alot.My sailfin tang has had it once..I have never treated ich with meds though.I use garlic,minced garlic that you can buy at the grocery store and some liquid garlic I also got at the grocery store and I mix it in there food.Garlic is supposed to boost the fish's immune system so they can fight off ich.As GMan once said a healthy fish can fight off ich,and that made sense to me,no one treats these fish for ich in the wild.My fish have always fought it off on their own with me adding garlic to there food.
Definately looks like ICH to me.. But DON"T TREAT the main tank.. Get a QT tank started.. Make sure you salinity level, PH and TEMP match your main tank EXACTLY before transfer.