Mine eat Innova too and it's the ONLY dry food Maddie will touch by itself...
It was mentioned already, but the Merrick canned food is really really good...mine LOVE it. It really looks and smells good enough for humans to eat, and that's a good sign to me! Their favorite is the Grammy's Pot Pie!!!
Maddie was slightly underweight at around 7-10 months. She's always been a really picky eater, and she was a really difficult puppy to keep weigh on...I worried about her constantly at that age. Her ribs used to stick out and her stomach was completely concave. When I took her to the vet last summer and I voiced my concerns about it he mentioned that free feeding (I don't know which you do) actually makes it worse. He suggested putting Maddie on scheduled feedings 4 times a day, and he said to mix in a couple tablespoons of a good canned food for taste. I tried and tried, and I went through about 10 different foods, and didn't find one until a few months ago (the Innova). He also said that lots of Yorkies go through a growth period around that age (she was 9 months I think) and they're so active that their metabolism keeps them from gaining any weight, even though their bodies are getting a little longer and taller. Now at 15 months she's filled out and she's a healthy 5 lbs even, and she's finally gotten a little tummy. I think it's really a matter of finding a food she'll stick to...even if you have to keep switching until you do...just be careful and don't switch her too fast or too freely, because it will upset her tummy!