I hadn't looked at RCs specifics in quite a while, two years? What I do remember from then was in order to get the most up to date ingredients and analysis, we had to go right to the source, RC. At that time they had changed the ingredients without letting their customers know. The retailers' websites had the old info.
There is the Yorkie specific kibble:
https://www.royalcanin.com/products/...-dog-food/3051
And what seemed to be the better formula that Yorkimom uses, this might be it:
https://www.royalcanin.com/products/...-dog-food/2447