Why Does Pieces Of Lambs Tail Keep Breaking Off?

We have a 3 - 4 week old lamb , male, who has arthritis in his joints. We have been giving him penicillin shots daily for it. He is being Bottle fed with Save- A - Lamb formula. Pieces of his tail keep falling off, is this normal? We have never had sheep before and I cant find anything about in on the web. We also just noticed after removing a metal tag from his ear that his ear is losing hair on the tip, not where the tag was. He doesnt have lice or mites, or ringworm. What could be causing this?