I would say if they've never been wormed it'd be a good idea to do it. You can buy stuff to mix with their food - think it should be done every 6 months. Have a look where you buy their food from you should get it there. Do you treat your coop for red mite ? That's another thing that might be affecting their laying - have a look for wee red spidery things on the perches, in the corners of the house or sometimes on the birds themselves, again you can buy stuf to spray in the coop from your feed supplier. Really bad infestations, I believe, can kill birds - so worth having a look.
If they've scratched all the grass up and you're able to move their run to fresh stuff that might make them a bit happier, but my two had been kept on concrete for a year before I got them and laid well - so doubt it would be that causing the problem.