Fertile Mystery ??

[MasterOfAllChickens111]

I have a hen that laid 3 eggs. All three eggs were fertile. The hens name is “Elizabeth”. Elizabeth had a man before the one she has now. She laid a egg and it turned out fertile. On the 2 day, the unborn chick had passed away. She gets one of my special roosters. She laid 2 eggs and they were fertile. On the 2 day, they both passed away. They both had different fathers. What might be the case here?

 

[SunHwaKwon]

How are you determining fertility and that they have "passed away"? Development isn't obvious until around 3 days of incubation.