My dog weighs 4:5lbs i feed her orijen mixed with pinnacle grain free is this too much protein for her?

She been eating orijen since she was 5 months old. In the last 2months I started mixing just to give her some variety....first I mixed with earthborn primative, then nutro limited ingredients also grain free...now pinnacle grain free.....so what should I do...is it ok to mix...should I stay with the same brand ...is this too much protein?