Hello and Welcome to YT. "Yorkies For Dummies" and"Yorkshire Terriers: A Smart Owners Guide" are excellent resource books .
You can go down to the bottom of the page and do a search. There is a number of recommendations for different food. Galen is finicky eater. I was feeding Taste of the Wild. Now I am feeding Fromm Salmon Tunalini. I like the grain free foods. You can also Check out
Dog Food Reviews and Ratings | Dog Food Advisor this will help with what is good and bad. Good luck