Of course you can tell whose egg it is .... you're their MOTHER!
hahaha, before my girls laid I thought "how in the heck am I going to know which hen laid which egg?"Not to mention a mother always recognizes the sound of her own baby's cry, even in a room full of kids! My neighbors always crack up when I point to the eggs and name the hen that laid each. I recognize their egg songs, too. Blanche is my loudest.
Until one day, my little pullet started acting kind of funny. I know who lays which egg because I sit next to the nest box while they lay it! I don't know whether I'm a human rooster or a chicken midwife.