Bboy's Mom, thank you for sharing photos with me of your boy. He is absolutely adorable. I would say you hit the jackpot on sweet face and overall cuteness.
I didn't see any cause for concern that he has a health issue that is affecting hair growth. He may just be in the awkward puppy stage, or he may not have inherited genes to produce a long Yorkie coat. As I wrote, environmental factors can also affect coat: activity, clothes wearing, hair products. Good food can also factor.
Unless you see something in his skin or he is scratching, I would not be concerned that his coat is indicative of a health issue.
Anyway, as promised, here is my sweet Teddy as a gangly, funny looking 8 month old:
