If you have your heart set on a certain size/look for your next Yorkie, you might want to consider a young adult. You'll know what you're getting then
Honestly, I can't believe that you spent so much on such poorly bred pups. You could have gotten a beautiful, responsibly bred puppy from a reputable breeder for much less. And who knows what you're getting when you can't go and see the puppies and their parents in person. They could be selling the puppies earlier than the recommended 12 weeks, so that they appear to be smaller than they actually are. Heck, sometimes the smallest pup out of a litter will turn out the be the largest as an adult, and vice-versa.
Take your time this time, and really research the breeder BEFORE you even look at their puppies. You're more likely to get a healthy dog and a good health guarantee from a breeder that's not in it to line their pockets. Read lots here to help you figure out what to look for in a breeder. YTCA.org is a good place to start, also.
Good luck!