I have around 18 hens that are 18 months or older. Earlier this summer I was given 4 chickens that had stopped laying for unknown reasons. Three of them (3 years old) were put in the stewpot after a couple weeks but the 4th one I promised to let her live out her days. Now my hens have almost stopped laying (only 4-5 eggs per day). I know that the shorter days affects them & I have a light on in the coop to give them the extra light. They are also just getting done with their molting so I am expecting fewer eggs until they are completely done. I have a concern though because the hen I promised to keep died last night for no apparent reason. She seemed to be perfectly healthy though I have no idea how old she was. Possibly 3 years old like the other hens that were given to me. My concern is this: is there an ailment that would cause a seemingly healthy chicken to stop laying eggs and if so can it be spread to other chickens? Any suggestions will help. Thanks