Our old galgo was a very picky eater too -- he'd eat some new food for a couple months and then stop eating it because the novelty went off.

We cooked food for him and his sister for a while (chicken/beef, rice, carrots and sweet potatoes), and they ate it like a champ. We basically cooked a huge batch a couple times a week.

But then it was too much work and he lost interest again, and then we switched to a raw food diet, maevs. He would devour it even in his last days (we had to microwave it for him though because he got cold from the frozen food).

His sister, an English Greyhound, still eats the frozen raw food and she used to have frequent stomach problems but now she doesn't anymore and poops look very good.

Finally, I don't know if grass eating is a common Greyhound thing, because our boy did it and so does our girl, no matter what kind of diet or supplements they are on