Hi there!
Feed wise, the chicks that are 2 months old should be on a growers formulated pellet until thy reach POL, at which point they get switched over to layers pellets. The growers formula allows them to develop physically at the correct rate. Everyone else should be on a layers pellet, unless they are moulting at which point they can be switched back to a grower's formula until the moult is over - that is because the growers formula is higher in protein - which they need in order to be able to grow their new feathers.
All birds should have 24/7 free access to unlimited feed, as well as to crushed oyster shell and grit. There should be multiple water stations available both inside and outside the coop. Fresh vegies such as cabbage, corn, lettuce, cucumber and the like are fine from time to time, as are additional treats of protein such as cooked egg, meat scraps and mealworms, but don't feed anything too salty or anything sweet or mouldy. Free ranging, if possible, is great for them - they can get access to all sorts of yummy bugs and worms, and the fresh grass will contribute to lovely yellow yolks.
I would recommend treating your flock for worms every 6 months (you can buy a liquid to add to their water to do this) and dusting for mites and lice on a regular basis. Obviously you need to provide a clean, dry, well ventilated coop, and some nest boxes with clean shavings or straw in it - one nest for every 4 birds you keep.
As far as egg laying goes, birds that are moulting usually cease laying. It should also be noted that as birds get older their egg production declines dramatically. It could well be that the 5 year old hen is no longer laying at all, and even the three year old hens will be reduced in their production in comparison to your younger pullets.
A final thing to consider is the changing seasons. I'm not sure where you are located, but if Winter is approaching and the days are getting shorter your birds will naturally start to slow down (or even cease) their egg production. To keep them laying you could install some additional lighting in the mornings and at the end of the day, but not everyone recommends that.
I myself like the idea of letting nature take it's course, and feel that if they are not meant to lay over Winter naturally then maybe they need that little break to get themselves back into good condition for the next season. That is a matter of personal opinion though.
Good luck with your birds. I'm sure some other more experienced chicken owners will have a lot of extra knowledge to add to this thread.
- Krista