I have two Speckled Sussex hens and one Black Australorp hen that were hatched late February 2022. They started laying at about 5 months old and were laying regularly until late April this year, then they all stopped laying. The Australorp is now laying 2-3 eggs a week, but the Sussex hens still haven't laid a single egg. Nothing has changed and they are very healthy, have good appetites and no parasites. Is this normal? When should I expect them to get back to laying?