Any kind of mastiff and giant breed in general doesn't need to ever be on puppy food. They need a quality adult or all life stages food that has the proper amount of protein and calcium to phosphorus ratio to prevent growing too fast.
---------- Post added at 10:28 PM ---------- Previous post was at 10:26 PM ----------
Also most specific formula foods (i.e. puppy, large breed, senior, etc) have you paying more money for that particular classification and are in most cases identical or almost identical to the adult formulas of that brand. An all life stage food (we use Earthborn Holistics Great Plains Feast) makes things simpler in that you don't have to worry about when to switch or if it's okay for your puppy or dog or senior. It's formulated for puppies right through seniors.