I have 2 Buffs, 4 Barred Rocks and Betty, a buff/bantam mix. Betty lays most every day, but the others - NOTHING. They are around 2 yrs. old and never really layed. They're fed cracked corn, laying pellets, oyster shell and free range in a large fenced area every day. I'm ready for them to go, but can't figure out why they are not laying. Any ideas?