My nutritionalist says that (I can give you her number if you'd like to call her and discuss your situation) small breeds under 10 lbs-roughly- mature physically at different ages. Nutrition can have as great an impact on a small dog as it can a large breed dog. She advises that you stop feeding a good quality commercial dry dog food to small breeds at around 13 months of age. These small guys have different dietary needs than most large breed dogs or even medium for that matter. Small breeds have a higher metabolism typically, a higher activity level and smaller organs to process all this. SO, while you would be encouraged by a nutritionalist to take a large breed puppy off of a good quality commercial dry dog food at 5-6 months, it's encouraged to take a small dog off at about 13 months. Not every dog is the same, use your best judgement and remember "everything in moderation" and if you ever hit a sticking point (like now), contact a professional w/ experience under his/her belt!
Hope that helped an ounce or two!
~yorkieK9trainer
(oh and w/ regards to treats, while you're feeding puppy food, it's best to give adult dog treats! Or you can go the healthy route and give carrots and frozen peas and things of that nature! jm2c)