Might consider the chance it's Ergotism. Caused by the ingestion of a parasitic fungus Claviceps purpurea. It's found in ceral grains, particularly rye and forage plants like ryegrasses.
Check your feed as that's the most likely source of contamination by Ergot.
I had some birds that had this a couple of years ago. I have my feed custom milled and two of the ceral grains I have added is red winter wheat and rye.
They had the same symptoms as yours, mine lived but if they get too high a concentration, it can kill them.
I had my feed anaylized and found out it was contaminated with the Ergot fungus.
