If you're following the instructions on the bag and you feel your dog is exemplified on the graph as healthy, you're doing fine. As my GSD grew, he'd go a week where he looked a little skinny and a week where he looked a little thick. Just growing.
Follow the bag and ensure he sticks around #3 on the chart and you're fine. It took me a second to understand that feeling rips and narrow hips is healthy for a GSD.
I never thought I'd own a German Shepherd.