Your babies are beautiful!!!!! As to your question, they look pretty small and may be to tiny to handle rats of any size at this point. My baby kings eat mice pinks and they are fine. (Sorry for speaking for whoever suggested mice)
Well if you want your Kings to get huge start them on rat pups (at the appropriate size) but as wizard said we cant really recommend much since we can't tell their size foreal. In my opinion it looks like they could down a rat pup but id have to know their exact size to tell you for sure.
1.0 Green Anaconda-(No Name)
0.1 Dumerils Boa-(Pandora)
0.1 Leucistic Texas Rat-(Luna)
1.0 Albino Texas Rat-(Jolly)
1.0 Hypo Everglades Rat-(Koba)
0.0.2 Black Rat-(Bonne & Clyde)
1.0 Ornate Nile Monitor-(Dracula)
0.0.1 Green Bottle Blue Tarantula-(No Name)