If he's scratching, I would not be surprised if he has some type of parasite... But it does not sound like velvet. My VT has a coppery color on his gills that shines under a flashlight, but its not velvet and he had no other symptoms. He was scratching when he had internal parasites, which I didn't figure out until after I QTed him in a bare bottomed tank (I could not see the white stringy poo because it was semi-transparent and blended in with the substrate). It caused slight bloating, as well, and his poo was sometimes white and stringy and sometimes normal looking.
Ich and velvet are not the only types of external parasites, either, though I don't have much knowledge on others.. It is frustrating not being able to figure out exactly what's going on. >:/