I have a year in a half yellow lab and i just introduced a beagle pitbull mix 7wks old two weeks ago. The puppy is very growl like and bites hard on her. I thought it was just a puppy thing but just last week i introduced a 8 wk old pit bull puppy to the mix too. and shes even worse with him. Is this normal for my puppy to be this way bc the lil full pit isint. What should I do?