Both of mine were under weight when I adopted them. I fed them puppy food and it put weight on them pretty fast. But Sierra will always be skinny. She is 60 lbs and you can feel her spine, ribs, hips, every bone. My vet has tested everything ($$$$$) tested for EPI (pancreatic disorder) etc, and there is nothing wrong with her, she is just a healthy skinny dog.

(She looks great with her winter fur, but I hate Spring time when she blows her coat, people ask me if she's sick because she's so skinny)

She eats okay.. she's a picky eater, she'll eat good for a few days, then she'll skip a meal here and there, then go back to being good.

Does Aspen eat good at every meal?? What I don't understand is why your vet would tell you NOT to feed her puppy food because she's still growing?? That's when puppy food is the most important. Plus she'll put weight on faster if she eats puppy food.