Velvet is a possibility, but often times early stages of Brook (very common in clowns) match the appearance of velvet. At any rate either disease would require moving all fish in the tank to a QT for treatment and a fallow period of 6 weeks with the DT to fully erradicate. The treatments are different depending on what you are dealing with.
Any other fish sharing the tank? Any symptoms or spots on the others?
Sorry you first post had to be in the disease forum, at any rate welcome to R2R!
https://www.reef2reef.com/threads/brooklynella.247938/
https://www.reef2reef.com/threads/velvet-amyloodinium-ocellatum.217570/