Rick is right about ACV - some people do give it to chickens as a gut tonic, and it is said to increase resistance to worms, though opinions are mixed on this, but it's definitely NOT an effective wormer. It's best to use Flubenvet, available on the Internet as a powder that you mix into a weighed amount of pellets and feed only this for 7 days. Flubenvet is the only wormer licensed for poultry that has no egg withdrawal problems, it's very safe and fully effective if administered properly every 4-6 months. You can obtain it as ready mixed pellets, but for so few little hens, this isn't economic as there will be quite a lot left over which will be out of date by the next time. The powder itself is easy to mix and a pot will provide 20 doses so will do your girls four times. However, if your birds have never had it, you should give them a course of it and repeat this three weeks later, as by then they may have further worms from eggs which hadn't hatched in their gut to be dealt with the first time round.
All chickens get worms, and can resist low levels of infestation if otherwise healthy, but a bad infestation can really pull a hen down and decrease her ability to resist other health problems. Worms can also cause egglaying problems, though I'm not saying this is the case with Pavlova. Hens can pick up worm eggs if eating earthworms or slugs, as these creatures are intermediate hosts for chicken worms. The worms hatch in the hens gut, and their eggs are excreted in droppings on the ground, which are either pecked over by the hens or eaten by the earthworms, and so the cycle is perpetuated.
So, as Pavlova appears OK in other ways, it might be worth worming them all and then reassess the situation. Was her laying normal last year, and has she been laying lots of softies his year, or just one or two?
There's an article on worming that might interest you on the main Poultrykeeper website, see
http://poultrykeeper.com/general-chickens/worming-chickens
Worms are only apparent in droppings if the infestation has got to an advanced stage. And if regularly treated with Flubenvet you shouldn't be able to see any. However, you have the option of getting the droppings tested for worms by sending faecal samples to The Chicken Vet for around £14, see
http://www.chickenvet.co.uk/shop/view/index.aspx/product/faeces-sampling-67
-but most keepers just dose with Flubenvet every 4 months or so.