I would get the best quality food you can afford. Since they eat so little, every bit of food is important that go in to these small ones, so this is an area to not skimp. Be aware many yorkies can have food issues, so try to steer for a good non grain food if at all possible.
A great web sites that truly evaluates all dog foods is
Dog Food Reviews and Ratings | Dog Food Advisor. Click on this link.
Here are the YTCA Michigan breeders from YTCA..
Sharon Griffin Lake Orion MI (248) 693-9327
Majestikyorkies@att.net PR
Jan Hamming Wyoming MI (616) 481-5053
Janhamming@aol.com
Pauline Hutcheson Fenton MI (810) 629-3966 / (810) 569-0910
pollyannes@chartermi.net S
Joan H. Lamborn Brighton MI (810) 588-6051
jhlppp@comcast.net
Cathy Lange St Clair MI (810) 4888-1080
Catlange@comcast.net P
Cynthia Mattoni Macomb MI (586) 466-3657
maitaiyorkies@comcast.net PAS
Vera J. Sheldon Melvindale MI (313) 381-8822
Jenilane60@aim.com PA
Cindy Warren Fort Gratiot MI (810) 385-3155
CYNWARREN@COMCAST.NET