Every dog is different. we have three Yorkies all with very different coats. Roxies coat is nice and getting long and seems to never have tangles. Madies coat always has tangles and doesn't seem to grow as fast, and Peter is the same age and has had his coat shaved off 6 months ago and it is already as long as Madie's.
It just depends on the dog. Also make sure not to brush his coat when it is dry. this will cause it to break of and it will seem like it isn't growing. Try spraying with some detangler or conditioner mixed with water before brushing.
__________________ Anna  & Roxy  |