Hi guys! My little guy is 9 weeks old Today and at his last vet's visit on Wednesday 9/16 only weighed in at about 3 pounds. I've looked at weight charts online and they state he should be at 6lbs by now. Could something be wrong with him? We didn't get to meet his parents and he was the last puppy in the litter so I'm not sure if the parents were this tiny. Do the puppies all grow at different rates? Big or little I'd still love him, I'm just worried there could be an underlying problem...