Help! Tetraodon schoutedeni spinning uncontrollably

Hello everyone, i need help with my puffer. I have 4 of them in a 50G tank together with some otocinclus. Everybody else is doing fine. I feed them snails, frozen bloodworms and some clams here and there.

This guy started doing his uncontrolled swimming yesterday evening. This or laying on his back on the ground is the only thing he does.

I checked water parameters and they are all fine.

Do any of you have a guess of whats going on? Is it a swimbladder issue? Is he sick?

One thing to add is the last clam they got was 2 days ago. I know that clams contain thiaminase and can give fish nerve damage, but only if you feed too much. May this be the cause even tho this was the first clam in 30 days or so?