Odd you say that. The friend I got the new rooster from asked me to look at her Pekins. She has 3 stunning blue Pekins that are just under 18 months old. 2 hens and a roo from show quality lines She bought them 6 months ago and they haven't laid a single egg,.They look as healthy as not moulting or anything like that so I wasn't sure why. She thought maybe they were a bit fat.
Over weight birds generally go off the lay also. Most illnesses will also lead to a cease in production. Even if the bird has recovered from a previous illness and for all the world appears healthy.