My dogs have always eaten grass no matter what diet their own. It's healthy and a way of cleansing the system. It could be that your dogs (I don't know what they were on prior to Innova) may be detoxing and are using grass as a way to help "flush" the system
As long as there are no pesticides or other chemicals used on the grass it's quite safe. You may also want to grow your own grass...oh
that doesn't sound right does it. Barley grass is an easy one to grow for dogs to nibble on.
Spring time is also a big grass eating time with all the new tender shoots coming up. My dogs have specific grasses they seek out and eat. They never throw up due to eating it, so for them it's enjoyable and provides a healthy array of nutrients including omega 3's