Blue Tangs, are you talking about Hippo Tangs or Atlantic Blue Tangs? If it's Hippo Tangs I would except them to probably not eat, and probably look to hide. You need to have something in the tank so the fish can have a place to hide. It could be anything for some pieces of PVC to rocks.
Did you just buy the fish, which is why they're in a QT or did you remove them from your MT?
Yes, it would be very common for Hippo tangs to hide, especially when you move them around to new tanks. You need to put something in the tank, like PVC or rock for them to have a place for them to hide. I wouldn't try feeding them that much in the beginning, as they'll probably wouldn't eat right away. Just place a small amount of food in the tank and in time they'll probably start to eat.