Check between the feather (esp near the vent) for mites.
Red mites check when they are roosting in the evening, run a bit of kitchen towel under the perch, if it gets red (blood) on it that's red mites.
Check the droppings for worms, or it doesn't hurt to worm once a month anyway.
It could well just be stress. Egg production is a month long process in the oviduct so if the cycle is broken it can take a while for it to resume (eggs can be reabsorbed into the body). Definately give poultry spice/live yoghurt/apple cider vinegar as a boost.

I got in a hen this spring that gave the others all of the above!!! Think egg production stopped for about 2 weeks.