I just read "Fur is dull and falling…" I don't know if my experience will be helpful . . . When we got Duke (12 wks old) he was in bad shape. Along with kennel cough, he had some bare spots on his elbows and ears and he was scratching!! The vet scraped both and looked for mites under a microscope - didn't see any. Three weeks later and another round of vaccinations and another scraping, there was no improvement. So the vet gave him a shot for mites anyway, and it cleared up in a couple weeks! He stopped itching, his fur grew back in the bare spots - finally I felt he was healthy puppy!!
Also, in regards to puppy's fur loss. I would think they would loose their soft puppy fur anyway as it is replaced by a coarser adult coat. Does that make sense? Just this summer (6 mo. old then), while bathing Duke, a whole lot of fur came out in the tub. I mean alot of fur. Would that be normal for an older puppy? He's got a soft full coat, but it's not the "fluffy soft" fur as it was when he was 12 weeks.