75 lbs at 6 months is way too much weight for a GSD pup to carry. This is the dog that wound up weighing over 130lbs, right?
Just a general statement for the novices and puppy owners on the forum: GSD's are medium sized dogs as a breed. Heavy, overweight puppies are not a good thing. One should strive to keep their puppy lean and in shape. Not fat and overweight. You should be able to easily feel each rib when you run your fingers down your pups side, like little "speed bumps." If you can not easily fell each rib, your dog is overweight. You should see a waist line when you look down at your dog from above.
German Shepherds are not measured by weight as a sign of quality. Bigger is not necessarily better and heavy, fat, overweight puppies turn into fat dogs and pay the price for their obesity. It is taxing on hips and joints and certainly takes it's toll on the dog. Too many well intentioned owners slowly kill their dogs with kindness.
I'm sorry, but this is a pet peeve of mine. It is a weird thing with many GSD owners to brag about the size of their dog, as if the 120 lb GSD is something to be proud of? It is similar to bragging about your 6 year old child weighing 200 lbs. People may agree that the kid is big, but is he healthy? Is he fit, healthy, in shape or just obese? Even worse are breeders that focus on the size of their dogs, and brag about how big the sire or dam is. A huge red flag IMO, and it means run away, run away really fast.