Best puppy/dog food?

I am not well versed with the RC specialty formulas for smaller breeds, but I would say offhand that if the RC adult works for your other dog, it should work fine for your puppy since (he? she?) would have such a tiny adult size too.  Another option might be to switch both of them to something like Canidae, which is complete for all life stages, then back again when pup is grown.  I suggest Canidae specifically because I've heard good things about it for the little coated guys on some of the mighty mite lists I'm on.  []

My concern when Zhi was a pup was growing healthy skin and teeth since both of those are an issue with her breed.  She ate EVO and raw meaty bones for the first six months, then I switched her to a combination of Natural Balance and home prepared with raw meaty bones.  She's the first itty bitty I've raised but either I'm lucky or something's going well.  She has all her teeth and her skin is perfectly clear almost all the time - very hard to do with a hairless.    Knock on wood!  Hey, does anyone have a smiley for that?  Actually, for me this one would work:  [sm=smack.gif]  []

Royal Canin is definitely much better than Purina One in my opinion. I think it's a decent food, and if she likes it then I would keep on feeding it.
 
I've been buying my Shih Tzu really awesome holistic foods that he's been turning his nose up at. Sooooo, I've found out that the best food in the world doesn't do any good if they won't eat it! Yorkies are also known for being picky eaters, so honestly if your dogs are eating it and doing well, I would stick with it!

Royal Canin Yorkshire is a decent food, better than Purina One.  How old is your puppy?  If he/she is younger than 6 months you'll need to feed Royal Canin Mini Puppy, which is specifically meant for small breed puppies.  The Yorky formula is for adult yorkies.