You'll soon realize (if you haven't already) that there is a lot of talk about which food is best for your dog... and sometimes the discussion gets a little heated! The truth is that there is no one dog food that is best; you need to just do your research, pay attention to any health concerns that your pup has, make sure you are feeding a puppy or 'all life stages' food (not adult) food, and do what works for your budget. I'm not familiar with the brand of food you are feeding now, but some general rules of thumb are to try to find a food without a lot of corn (many Yorkies have problems digesting this) or other fillers. I personally try to feed my dog as natural and healthy of a diet as possible, including no gluten and little to no grains (fillers), no preservatives, artificial products, chemicals, stool hardeners/softeners, animal by-products, etc. I feed Meg "The Honest Kitchen" and I'm sure you'll get responses from people who feed Canidae, Nature's Variety, other kibble varieties, raw diets, homecooked diets, etc.
If you do decide to switch your pup's diet, do it slowly. First mix 75% old vs 25% new, then slowly increase the ratio.
Again, just do your research and then pick a food that you think is good for your pup! It's a daunting task, but you can do it!
