I have one barred rock hen almost 2years old according to breeder I brought her from. She lays a fart egg about 20mm round about every second day. No yolk, but nice strong shell. Is she ok? Will she start laying big eggs? Can I help her? They get pellets, wheat, oyster shell, 'chook chow' ( a mix of seeds, oats, molasses, maize etc) and they free range around the house and farm most afternonns.