My juvies grew like that too. They were barely 2.5" when I got them, super skinny. Three weeks later they're 5" and look like your king.
I just got a new one a few days ago, he's tiny and I'm not going to house them together until he catches up. Which could be a while, if ever. You could use a divider. That's what I'll probably do when my new guy comes out of quarantine. You don't keep them in those small containers do you?