If you can count the dots, it's ich and I can definitely count the dots on your Tang so you have ich.
However, velvet can LOOK like ich at first, and then BAM! Next thing you know is the fish is completely covered and you can't count the dots anymore; that's velvet.
Put all fish in a QT with either cp or copper and it will kill the problem for both ich and/or velvet. If one fish has it, they all have it. Good luck.