As your chickens are 'old' commercial stock..they would not have established proper 'life cycle' for the feathers yet..the life in 'factory' environment is so different to being in 'home'. It is quite possible them starting moulting this time of the year. Usually you would expect see moulting end of summer..but I suspect next year they will be moulting a bit later..

Previous recommendation for extra protein is correct..they will need it so they have the 'energy' to grow the new feathers..sooner the replacements have grown...sooner the laying comes back.
Although mealworms are not quite practical for chickens as protein as they would need to eat them quite a lot and it will lighten you wallet too.
Easiest way to provide extra protein is giving them some dog food..either moist can food in loaf form..no jelly, gravy or chicken...or..get some complete dog bisquits..something like lamb and rice or beef..soak them in boilded water until soft...they will love it!

Other than that you could dig some worms, collect some snails and crush the shells..chickens will sort the 'meat' out of shells.
Some years chickens only go through partial moult so there is not that many feathers about..and every so often they do it properly...now it is quite alarming site when they go through 'proper' moult..they do look like they've been prepared for a pot, but still alive
