Medium Breed puppy food vs. Large Breed

I have a female Golden Retriever puppy, exactly 4 months old today. One week ago on a borrowed scale, she weighed 12.4 kilos. My question is in regards to food. We are feeding her Purina ProPlan MEDIUM Breed dry puppy food since a Golden Retriever is on the package front (we just bought a big 15 kilo bag). Now I am concerned that we should have bought the LARGE breed formulation. We are currently in South America, so I do not know if the formulation is different here than in other countries(?) In comparing labels, the diference is as such: MEDIUM BREED: Crude protein min 29.0; Crude fat min 18.0; Crude fiber max 3.0; Calcium min/max 1.0/1.4; Phosphorus min/max 0.8/1.3. LARGE BREED: Crude protein min 28.0; Crude fat min 13.0; Crude fiber max 6.0; Calcium min/max 1.0/1.4; Phosphorus min/max 0.8/1.3. So, the MEDIUM breed formulation has more fat, a bit more protein, half the crude fiber & the exact same calcium & phosphorus as compared to the LARGE breed formulation. Is it a problem if we keep her on the medium breed until the 15 k bag is gone, then switch to the LARGE breed formulation? Will this harm her development? Thank you!

Hello - I am not going to pretend to be your dogs' dietician and have not looked at the ingredients.   However, we would strongly advocate speaking to the your vets or those at the pet food company for this one.  I would never feed a full bag of something I knew not to be nutritionally right but no wolf eats such a finely tuned diet in the wild.  The question is what the impact is likely to be.  Its worth saying that there are pet foods that are completely inappropriate being sold every day - the petfood industry has been very poorly regulated - and this may still prove to be a better choice for the given patient than most of them.  If you and your vet do decide that the choice is okay, then rather than finishing the 'incorrect' bag over a week / few weeks, it may be better to weave the 'incorrect' diet into the main diet - eg alternate, or every third day.  However, my main advice here would be to chat the implications through with your vet, who knows the diets concerned - as I do not.