I recently adopted another puppy. She's a 9 week old Beagle/Lab mix named Ally. My question is what I should watch for as far as playing between her and my 6 month old Beagle/German Shepard mix Diesel? They seem to get along great so far and are always following each other around and playing. The one thing that concerns me is that Diesel will tend to try and bite at the back of Ally's neck. I never hear her yelp like it is painful but I have been punishing Diesel for doing it. Am I being overly concerned? Any other pointers or things to watch out for?