If they are 2 years old, egg production may well slow right down or even stop.
I think this is more likely the answer if the birds seem in good health.
pol they where only 17 weeks when i got then from the farm its been going on for about a week now am thinking about flubenvet but they where wormed in march so really dont want to do it sept.would some acv be of any help? only had 2 eggs today and they are good shells.
A week is not that long - it could be something changed, maybe a stress factor such as a weather pattern shift (eg too hot, thunderstorms), maybe coming into moult, a new visitor or something unfamiliar.
Worming them might not necessarily have anything to do with soft shelled eggs but it might be worth treating them so that you can tick the box as done and be sure that it is not the problem rather than whittle about it for another couple of months.
Calcium is insoluble in acidic conditions, so perhaps ACV is not the answer here. I'd go with earlier suggestions and add a little limestone flour to a mash meal (maybe with a small amount of cod liver oil - if nothing else, the vitamin D will help to strengthen their bones if there is a calcium absorption problem) as well as some dark leafy greens (perhaps avoid spinach and chard as these contain oxalates which bind with calcium) If they have been having other treats, it might be an idea to cut these out as they could be feasting on those and not so much on the layers.
Talking of layers pellets - maybe give the sack/bag a good shake of the the contents as sometimes the supplements can settle down to the bottom giving an uneven distribution.