Yes, hours of light is presumably key to laying. "They" say you need 14 hours of at least low light to keep the hens laying through the winter. That doesn't quite add up though because my girls start back up about the end of February and we don't hit 12 hours of daylight until middle/end of March.
I think increasing or decreasing light causes different effects than constant light.
And I don't know how you are counting hours of daylight, but the chickens might be sensitive to lower levels than what you were counting. Any source that measures from sunrise to sunset misses twilight (which is very short near the equator, but can last for quite a while when you get out toward the poles.)