Feed him/her something smaller than a mouse at that age.

I fed my new fire a small sized mouse (aka the smallest I could find at the pet store, which was like a hair sized smaller than all the other adults ~_~) and I found a dot of blood in her container, then when I went to check her out I saw that the little split in her scales where she had been connected to the yolk in the egg (the snake version of a belly button) there was a little tiny scab under it, leading me to believe that she had actually split open slightly because the prey item had been to big for her. Never again will I feed such a young snake so large a prey item, that had me freaked out and I was sitting around ready to go to a vet if there was any other sign of trouble (like another spot of blood). So be careful, and don't overfeed/outsize feed your snake.