I have a 2 month old silkie that started having episodes lasting 30 second, up to 2 minutes, he bends his head down under his chest and walks backwards. He hold his eyes closed and his neck feels stiff. I've noticed these occur if he gets freightened but sometimes with no trigger. There has been no change is feed and the feed is high quality. He was hatched in my incubator and raised in-doors in a brooder with other chicks from the same clutch. None of the other chicks show any symptoms and seem very healthy. Any ideas?