you will get lots of different opinions on this topic by different members, but I will tell you what I do. A lot of people say chickens require 14 hours of light. so I have a light in my barn (I have an in barn coop) it gets pretty dark in there so if I didn't have one it would always seem like night to the chickens. My light goes on at 530 am (the time where I have learned they wake up and make so much noise I can actually hear them from the house) and it goes off at 7p.m when they voluntarily go to bed on their own. My Dh wanted to give them a Flood light, I stopped him cause well I don't think super bright light would be all that good for them. Before I decided on which times to set the light to go on and off I had to learn my chickens cycle. 
If during the day you got good natural light int he coop you will likely only need a couple hours before sunrise and a couple hours after sundown.  
It seems like the to light or not light issue is very much split with BYC members, some prefer to provide the 14 hours of light so the chickens keep laying, some prefer to allow the chickens to live as naturally as possible even if egg production slows during winter. Its all on personal choice. 
what are you feeding your chickens? how old are they? can you provide more info, just before they stopped laying was there any change to their diet or living conditions or did you add any more to the flock?? did they go through a stressful event? in any event I am sure this is just a temp thing and they will go back to normal as soon as they feel more comfortable.