So in the last month my male, 17 month old, GSD has began being really short tempered with puppies. He's got into it with four puppies. All about one year old. The last one was with a Mastiff that was huge! The puppies bite back if he bites, he only did twice and no damage done, no blood. Then after it happens he is very submissive to me and pretends like nothing is wrong. The only thing I can think of is he is getting older and when this happens I'm holding his favorite chuck-it ball. Is it the ball that is causing him to react poorly to puppies? Some puppies he does nothing to even when I'm holding the ball. Two of the puppies would jump around him, but not even touch him. Please help. Thanks!