I have two chickens that share a small coop. They are 9 months old. The Red sex link started laying in June the Plymouth Rock in September, last week one of them laid 2 eggs in one day but one of the eggs was translucent and not completely formed. The next day we were an egg short, the next two days the egg shell was so thin that it cracked before we got to it, we had a day where the egg was thin shelled by ok, now today the egg feels like cardboard. The other egg is fine. Guessing by egg color I would say it is the Plymouth Rock. What is wrong???