Your chickens can't tell time. To them, nothing changed. There are still the same number of daylight hours as there was before we set our clocks back -- daylight is still slightly waning in the northern hemisphere, but there was not a sudden quick jump of an hour.
If you're still letting them out at the same by-the-clock time however, that could be making a difference in how many of those daylight hours they see. And if your coop doesn't have windows that could make a difference in their laying productivity.
Just as an example here, before the time change it was getting light at 8:00 am and dark at 7:00 pm for a total of 11 hours of daylight. After the change it gets light at 7:00 am and dark at 6:00 pm for, still, a total of 11 hours of daylight. BUT lets say you let your chickens out everyday at 8:00am and they go to bed on their own at dark. Before the time change this means they were seeing 11 hours of daylight, after the time change (because you're leaving them in for an hour after the sun comes up) they're only seeing 10 hours of daylight. Make sense? Could this be what's happening with your flock (you let them out according to the clock, not the sun and your coop doesn't have windows)?