The top third of the ear is usually shaved, so I'm not sure your dog has any less hair than normal. Silky coats tend to have thinner hair then cotton coats. The bridge of the nose concerns me, and you could have the vet do a skin scraping to be sure that there are no mites, but it could be just hereditary, have you spoken to his breeder? I don't think it's diet related, he has fabulous hair elsewhere. Personally, I think he's beautiful. I would just trim up the ears!
