I have four pullets, and they have all been laying eggs steady for about two months now. four eggs everyday, once in a while three. Every egg has always been layed in the nesting box. Then tonight when I went out to lock the pop door on their coop (free range chickens) and check their feed/water, I noticed a soft shelled egg on the floor of the coop. No shell what so ever, almost like a rubber shell. They have crushed oyster shells and have been on layer feed since late summer just before they started laying. Is this normal for a hen to throw out a softy once in a while? Why now out of the blue?