Unless you are using artificial lights, they will tend to lay more eggs in spring & summer than in fall & winter. If you're working from full-year averages, then it's not surprising if they underperform at this season. Yes, it is somewhat likely that you will get a stretch averaging 17 eggs/day...
Have you checked their butts to see how many are actually laying?
I've had a batch of chickens where the first was laying more than four months before the last ones started.