I have a border collie/red heeler puppy. He’ll be 5 months on the 23rd. I got him when he was 8 months, and he had grown normally until about 3 and a half months. After that, I haven’t really seen much of a difference. I’ve seen both border collies and heelers his age and they seem a lot bigger than he is. Is this normal? He eats enough and doesn’t act strange or anything.