Well, the Blue Buffalo formulas are AAFCO certified as 'Maintenance' formulas, but for the life of me I can't see why ... From the nutritional information listed on the Blue Buffalo website it looks as if either of them could easily be labeled as 'All Life Stages' foods, and the calcium and phosphorus levels look perfectly fine for a GSD puppy.
The Natural Balance formula is quite low in fat at just 10%, but the AAFCO certification for a growth and development food (that is to say, safe for puppies) puts the minimum fat content at a mere 8%, so technically it is fine for puppies.
California Naturals is a very good food, and they make quite a few different formulas with some unique protein sources (kangaroo for example). Some of their formulas are more suitable for a large breed puppy than others though so check the nutritional info before choosing one ... Their website has a huge amount of nutrion info about each formula, as do all of the foods made by Natura.
If the itching is your only concern though you may want to try simply supplementing with some fish oil first and see if that helps before switching foods too much and too often. Puppies tend to be pretty sensitive to diet changes and too much switching may result in upsetting the digestive system.