I have had 4 eggs with fully developed babies. Die. They just stop growing! They have wings, bills, cute little feet, and feathers. but, Dead. Their approx hatch days come and go without as much as a shaking egg. What is HAPPENING??? They are in a LG still air incubator, I turn them 3-4 times per day (except on lockdown), humidity and temp are good, but they just stop. I have one duckling that hatched 2 weeks ago and he doesn't have a ducky bud because they keep dying. HELP?!