At 7 cups a day, I would certainly agree it might just be time to try something else.
Seeing the ribs a little bit is fine, this is common for most adolescent GSDs and nothing to worry about. Seeing the ribs prominently/hip bones prominently, however, is not ideal. If that's what's going on, I would switch to a higher calorie, higher fat food.
Nulo Endurance is what I used to help put a little weight on my youngest, and I was generally pleased with the results. Its a 20% fat/466 kcals/cup food, plus very good quality and completely chicken/egg free.
If I were you, I would look for foods that are closer to 20% fat, with at least 400 kcals/cup. If you can't find else can't afford a dry food like this, consider supplementing with things like beef trim, dark meat chicken like thighs/leg meat (with skin), pork shoulder/fat, etc.
GSDs- Mulder, Ridley, Vega
GSD on the half shell- Rigel