Ask any German Shepherd owner about their dog's stomach and you'll probably get an eye roll. GSDs are notorious for sensitive digestion. Loose stools, gas, you name it. Finding a food they tolerate can take trial and error, but foods with added probiotics tend to help.
On top of the stomach stuff, GSDs are prone to joint problems. Hip dysplasia is practically endemic in the breed, so glucosamine and chondroitin from day one is a smart move. Their deep chest also puts them at risk for bloat, which means smaller meals spread through the day instead of one big feeding.
They're working dogs at heart, and that muscular frame needs real animal protein, not grain fillers. Look for something with chicken, beef, or fish listed first.