I agree they are likely not mature enough to lay yet. I don't even start to expect a first egg until week 24 and had some Orpingtons once that waited long past 30 weeks. That was depressing and no longer keep them.
I didn't use lighting this year and can affirm that it makes a heck of a difference. When we did use lighting it was an energy efficient 18w flourescent bulb in warm white. We had it on a timer to provide 12 hours light total. The timer allowed several switch on and off so had it turned on at 5 am and then off at 7 am, on again at 3 pm and off at 5 pm. That way I never had to adjust the timer and could let the day light dwindle and gain knowing they had 12 hours of light. About March we get up to 12 hours of light again so took the light out.