Nymphs cannot lay eggs, therefore, the eggs must have been attached to plants you got from this seller. I would just remove those plants and I'd be fairly certain the damselfly larvae would not continue popping up. If the shrimp are already removed from the tank, you could try adding some small corys or Amano shrimp to clean up any eggs still in the tank that might have detached from the original plants. I wouldn't nuke the tank if it was one of mine. Good luck!