From my point of view, pedigree and other kibbles/dry dog food are like burgers and pizzas for humans, burger and pizza can be good if we take it for one month/year but think what happens if we take this lifetime? Is that good for our health? similarly for dogs you can give dry kibbles as alternative for main food but not as main food.
You can do some search in internet and try to find out what homemade food suits best for GSD. Also while giving home made food to your GSD, you will be knowing what your dog is eating, but in the case of dry foods, we always choose brand based upon the ratings, and the brand with highest ratings are costly and not affordable by the normal middle class families also the brand with nominal price suits for some dogs and cause allergies (as most contains grains) and organ failure to some dogs and that made shorter life span for dogs. Also while giving dry kibble food you should make your dog to drink plenty of water but some dogs wont drink, and this made tough task for us to run behind our dogs to make him drink plenty of water.
Either you give home made food for your GSD or put him BARF/PMD diet that will be the best food for your GSD than the brands you mentioned.
Remember that dogs are like kids and stay as kids lifetime, they will eat whatever we give just like human kids, but we as responsible dog owners/parents should give right and healthy food.
My friend has GSD and he is giving beef rice daily and the dog looks awesome and healthy. My lab is on BARF diet and his meal have only chicken, lamb, egg and yogurt. I dont go by vet advice as my vet told me raw meat food bring animal agression but my lab made this statement false.