Mold is just a guess.
Mold can cause neurological issues. Here is an article from McMurray Hatchery.
https://blog.mcmurrayhatchery.com/2014/09/18/mold-in-the-feed/#:~:text=In%20the%20acute%20form%20in,other%20forms%20of%20nervous%20symptoms.
As soon as I had a chance, I would look at the...