Hi,
How are you measuring and controling the temps? Overheating can also cause neurological symptoms.
Your temps however sound a bit low - I aim for 90-94f inside the hot hide and 80-82f on the cool side.
Does he have any boas or has he added any new snakes recently?
Has he treated for mites or any other household pests?
Has he sprayed anything in the room or changed anything in the snakes environment?
dr del