Hey Alyssa! It's good to see you again, but I hate that it has to be this way.
The first thing that comes to mind for me when I hear a story like this is some kind of chemical contaminant. Is it possible that the snake was exposed to some insecticide or cleaning agent? House paint or thinners or aerosol spray? Even computer "canned air" can be dangerous. All sorts of things.
The other thing that comes to mind, if everything else is ruled out, is a tumor somewhere on the nervous system.
But these are just guesses. I don't have any medical training. I'm afraid this isn't something anyone here can help "fix" but maybe we can at least arm you with enough questions to help a vet figure out what might be going on.