worried

So me and my husband have 3 sweet baby rats (2 to 3 months old) and today we came home and one of our rats Benny had what looks to be blood on his back and this weird substance stuck to his fur we got the stuff off of him but it looks like his back where the little bits of blood are hurting him...

I just got a new naked rat, I put him in with three other boys (after intros), one is neutered... The 2 intact males don't bother the new guy even when he is terrified and screaming. New guy is mostly blind because he has very light pink eyes.. My neutered male had been seeking the new guy out...