I would crate the puppy when you're not home. Leaving them unsupervised could be a recipe for trouble.
Also, do not allow your puppy to harass your older dogs.
Agreed.
It might just be annoying now, but it can be a real problem when your GSD grows up. Trust me, we just re-united our GSD with a small chi-pom and the little nipping that goes on, is pretty terrifying. It took a good solid two days of constant work to get the GSD to leave the little one alone.
Come up with a command for the dogs to leave each other alone, and enforce it. Try a small spray bottle filled with water and a capful of vinegar, it should stop the behavior dead in its tracks. Be clear, fair, and just one spray will do it. The command should be universally understood between all the dogs. Even the little ones can't pick on each other.
