You are NOT feeding him a balanced meal. Can you MIX the kibble with small portions of the eggs/yogurt/chicken? So the balance of the meal is the kibble and you just use the 'other' to get him eating.
Be aware, that MANY of our GSD's are just picky eaters and will go days without eating just cause they don't feel like eating 'boring' food. We have a sticky with many great ideas that have worked for us ---> Pup doesn't want to eat (picky eater?)