have you checked his selenium? In one of our arabs, you can tell he is low on his selenium intake because he starts acting like a spooky bastard, nothing can bring him down. We he was a baby we thought he was just mentally challanged because sometimes, for months at a time he would be great. Then BAM, it was like death stalked his every door. When the spring grass came in, suddenly he was a doll for awhile again.

It's around $60 for full bloodwork to be done with my vet, don't know what it is with yours. Couldn't help to check though.

Sorry if someone already mentioned this, can't read every word because my boss keeps looking over my shoulder.