i have about forty chickens and they are free range and have a 8x10 coop.....i went out yesterday and found an egg that is my brown layers and it had two large circles that were darker then the brown egg...they dont wipe off when being cleaned...the chickens are about a year old....the one is on the not so pointy end and is about a half inch round and the other is in the center of the outside of the shell and is about one inch long and half inch wide...any ideas