I heard a strange noise in the box with snakes, a snake was convulsively twitching like a earthworm. I put it into a separate box, other snake was ok. 3 days before that I fed them, and everything was ok
The patient had convulsions about once every 1-5 hours.
The vet told me by phone that it is or intoxication or "a parasite" and if others my snakes are feel good (I have 4 garter snakes),then it is "a parasite". And he couldn't help....
Other dude told that it seem like "Thiaminase Problems".
Last 6-12 months I fed them "safe fish"(Tilapia), but recent 4-5 time it could be "unsafe fish". (Also I always added a little REPTIVITE with D3).

On his advice, I started doing injections of thiamine(vitamin B1). Periodicity - day and 5% solution of thiamine about 5 mg/kg weight of snake.
The convulsions were finished after first injection. Snake began to shows tongue and became more lively....
I have done 3 injections, but snake did not feel better...

I noticed "something strange" near a head of snake...
https://www.dropbox.com/sc/lth4rurzx...j83qKXQwpNhSZa

A short video, but he could be more active
https://www.dropbox.com/sc/2asorvsoe...-5J_bzNLVO-kUa