The AAFCO statement on the Pro Plan 30/20 bag says "Animal feeding tests using AAFCO procedures substantiate that Pro Plan Sport Performance 30/20 Formula provides complete and balanced nutrition for all life stages of dogs including growth of large size dogs (70 lbs. or more as an adult)." (which is where I got my "70+ pounds as an adult" from).The calcium and phos may be ok but there is no way a 30/20 is ideal or generally safe for a large breed puppy. Plus the vitamin and mineral balance are for an adult dog, not a puppy. You only feed more or less of the salsa ratios. Also, it is an all life stage food with means be definition, it has to meet the requirements for the small breed puppy with us significant more then the large breed puppy.
Plus that food is for a working dog that is in the field for 4-6 hours. There is no way a puppy 8, 10, 16 weeks of age will ever need that much extra.
Also the definition of large breed puppy is 50lbs and above, giant breed is 100lbs and above.
You were feeding a food that was at the to end of protein and fat for a large breed puppy. 30/20 is on the extreme. Plus it's not 100% you will get joint issues but certainly you increase the chance a good bit. It would be better to feed an adult food than an all life stage food.
A search of the AAFCO website tells me this means that the manufacturer not only put a sample of the food through laboratory testing to verify that the food meets AAFCO nutrition standards, but also put the food through AAFCO-standardized feeding trials. AAFCO protocols give a set of parameters for the feeding trials including length of the test and diagnostic tests which determine the success. The FDA website tells me that this specific nutrition adequacy statement essentially guarantees that the food was found to provide proper nutrition. Since AAFCO and the FDA are currently the US's leading organizations on pet food, I'm inclined to trust them when they say a food is OK for large breed puppies.
Since your opinion is clearly different, I'm curious if you can provide any studies/research that indicate an all life stages food is NOT suitable for large breed puppies?