They can really make you worry, can't they? Gus will even turn his nose up to home cooked food sometimes.
Quite a few people home cook for their dogs and have shared some great recipes (and book suggestions). Look in the Yorkie Health and Diet section. Here is a link to one of the sticky threads...
http://www.yorkietalk.com/forums/showthread.php?t=75933
Welcome to YT.
I just noticed your avatar. Your yorkie and cat are beautiful.