Premium Feather Member
Possibly something came by and scared them last night? Could an egg malfunction happen in a day like that from fright?
The possibility of them being stressed by a predator seems likely to me.
Do people in your area use firecrackers or gunfire to celebrate holidays? If so, noises in the night of that kind might have upset them.
Or it may be one of those weird things that happens sometimes with no real explanation.