King has super flaky skin on his shoulders/neck. I'm 99% sure it's from a deficiency in something...maybe zinc? He has Purina goat mineral free choice and has had a cobalt block free choice since May 22nd 2021. He just got copper bolused 9 days ago. No lice. He drinks well water and gets 1.5 cups alfalfa pellets, 3/4ths of a cup beet pulp pellets, and 1/2 cup Purina mini horse and pony grain daily. Pics were taken 8 days ago. Any advice?