size of lab

Question
We have a female black lab that is 7 months old. I adopted her from my brother who is a breeder, and several of our friends also took a puppy from the litter. The problem is, Maggie has filled out (she's about 45 pounds), and is not skinny or fat, but she's really short. She's much smaller than her mom or dad. Everyone that sees her asks how old she is, or what kind of dog she is. We have fed her the amount suggested on the side of the puppy chow bag since we brought her home, but my dad insists that's not enough. THe other puppies are now twice her size. She also was not the runt of the litter. What I'm wondering is, could we have stunted her growth, but not her body length, by not feeding her enough food? If we double her feedings at 7 months, will she grow taller, or just fatter? When do labs get their full height? I've had smaller dogs in the past, but this is the first lab we've owned. Other than her height, she's been to the vet regularly and is healthy.
Thanks,
Amy B.

Answer
This does seem a bit odd since you did get him from someone you know and know the dogs that he has there is little chance that the dog isnt purebred....it could just be bad gentics...not every pup in the litter would show problmes such as breeding poor quility not show quaility dogs together or dogs that are closly related to each other. My lab grew normaly she was full height at 9 months and fullly filled out by 14 months.