Hello everyone, I have 3 duck eggs in my classroom incubator. I candled them on Friday, 4/25 and they were all moving. They have four days until hatch date. I checked them today 4/27 and two of the eggs had a grayish spot on the outside of the egg that I am pretty sure wasn't there on Friday. I candled them again and I did not see movement, but the air space had gotten larger since Friday. The 3rd egg that does not have a spot still had movement today. Do you think they are ok? My Pre-K kids are so excited