I have used Purina Pro Plan Large Breed before with mastiff breeds and it was fantastic and if a little bit of extra weight is needed it might be worth trying a couple of months on the puppy formula.
That being said I have also had dogs that have not done so well on pro plan yet have thrived on Eukanuba or Advance.
At the end of the day all dogs are different, I think it all come down to trial and error, try a few different things and eventually you will find what works best for your dog.
Cheers,
Talbriah