Switching my 4 1/2 month old German Shepherd's food from Purina Large Breed Puppy formula, heathy suggestions?

I have a female German Shepherd, 4 1/2 months old. I'm looking to change her food from Purina Large Breed formula as it's gotten to a little more than 1/3 left... The original food was suggested by the breeder, so I kept her on that while her transition was made. She's been living with me now for about a month and a half. Any healthy suggestions on a new form of kibble available that is trusted and a healthy choice for her (preferably in Montreal) Thank You!