Im not sure what Marine Velvet looks like but i was up late tonight and this mornign and reasearched a alittle for you and i have included a couple threads that might help in the id of the disease u have asked about. https://www.saltwaterfish.com/vb/show...=Marine+velvet https://www.saltwaterfish.com/vb/show...=Marine+velvet
I dont know much about Marine Velvet so im not much of a help hopefully the links posted above will!
Rich