I have a flock of two year old Buckeye chickens. They have been, and still are, great egg layers. One problem I've had since the beginning of them laying is that when you crack their eggs to cook them, almost all of them will break (not hold their shape). Is this a problem related to diet or possibly freshness? They are free range and eat 20% layer crumbles, corn. wheat and vegetable scraps. They also receive oyster shell and the shells are never a problem. They graze all day and have access to whatever greens and natural foods their hearts desire. Any suggestions are much appreciated.