Could be a number of reasons, and probably a normal condition. Breed? Or Breeds, if you keep a mixed flock-- Feed and housing? How long since their last eggs?
a hen that has layed a "clutch"--her normal number of eggs before mother natures says "set and hatch" (and is not a "layer" breed or hatchery "production" hen-that have that natural rythm bred out), will either set (rooster or not) or just take a rest. Laying eggs regularly, is a great drain on the hens--and a rest allows time to renew. (Hens produce a "baby chick" every day or two--have you thought of the nutrition needed for that?) If fed well, GOOD Layer Ration, and free choice Oyster shell/and grit, clean water, dry coop or "clean" pasture, hens should begin to lay again and depending upon BREED, may produce well for several more years (fewer eggs, but steady laying). Not to worry, Good Luck,