Runts happen.
In my clutch of 11 from last year - one of them was same size as others out of the egg but just is not growing very fast at all.
Here she is next to a clutch mate - they are in same shelf of same rack:

Your king may be breedable.
I don't intent to ever breed my runt, I'm planning on giving her away once she is a little bigger (I want to make sure she doesn't have something wrong that will result in early death). But it happens.
Have a fecal float done, some parasites can result in stunted growth.
-----
x.y L. getula californiae (Cal. King)
x.y L. getula nigrita (MBK)
x.y L. getula floridana (Brooksi)
x.y Pantherophis guttatus guttatus (Corn)
0.1 Pituophis catenifer catenifer (Pacific gopher)
0.1 Heterodon nasicus (W Hognose)
x.y.z Elgaria multicarinata multicarinata - (Cal. Alligator Lizard)