How old are they? If their old they might not lay eggs consistently or they could be completely done laying. Also in the winter it’s not uncommon for chickens to stop laying eggs due to the reduced amount of daylight. If you add a light source to their coop that should help get them laying again.
Are they molting? They will lay less eggs during a molt. Low light levels also causes them to slow down laying. You can put supplemental UV light in the coop to get them to lay again. Make sure they don't get over 16 hours of light if you decide to do this.