I'm going to have to disagree. They are 3 years old and you said, "they cranked right up". That to me shows they had the enthusiasm and will to do what they were bred to do from the very get go once they were released. If they are not showing that same enthusiasm to scratch after cranking right up AND not being hurt at all, for less than 15 min, then on my yard they would be culled. I also don't consider that a game check in any form from your description. However, I don't know your line and what is normal for what you feed. If it's common practice for your dogs to need to the age of 3 to know for sure they'll start, then maybe then aren't started, but the scenario you gave to me implied otherwise.