Make sure your humidity is raised to the 70% range. Some mist the duck eggs, they like plenty of humidity. That does not seem feasible with a mixed bunch. You might place the duck eggs on a damp paper towel. It will dry quickly if you have a forced air incubator. If you can add warm water with at straw or piece of tubing through the vent hole on top. You will not need much just enough to dampen the towel.