If they haven't pipped externally yet, candle the eggs, mark the air cell line and create an artificial pip hole above the air cell line. The safest way to do this is by taking a sharp object and scoring an X over and over until you can break through the shell, then take a pair of tweezers and carefully break off a little bit of shell to make the hole. Make sure you break through the outer membrane as well, but don't touch the inner membrane that is covering the duckling. Once you have this pip hole in place leave the ducklings for a few hours and check if they make progress from there. Good luck!