Potentially you are gonna need to up your feeding either by size or more frequent feedings. After that sometimes just picking them up, holding them, let them bite and do whatever for a few minutes they may calm down a bit then place them back.
Worst case scenario you just deal with having an angry snake. A king snake never gets to a dangerous size to cause real damage and you'll likely learn some new respect for snakes and other handling sessions with other snakes will be a breeze.