Hi and welcome! It could be hormonal, or if your new boys haven't been handled much, they are probably just being defensive. Drawing blood means they are afraid and don't want to interact yet. Don't put your fingers near their faces for now. Try feeding a wet treat like cereal or baby food on a metal spoon, and encourage them to come to the front of the cage for their treat. They will learn to not bite the spoon, and you'll be able to talk to them and let them see you better and smell you (they have rather poor eyesight). As they learn who you are, and how to lick the treat, you'll see them start to relax. It can take weeks for them to become familiar and feel safe in their new home. Time, it just takes time.