I was not one for routine worming, but if they haven't been done for a while, or seem to be eating more than you might expect and a bit thin, it might be worth considering. Also check round vent and under feathers for lice, and check the house at night for redmite.
Shorter days is the most obvious problem, but also predators can be a problem. Foxes prowling at night [size=78%]can put the birds off lay [/size][/size][size=78%]or rats in the house will upset them, as not only do they unsettle the birds but will take the eggs as well leaving less for you to collect. [/size]