Any "dual" non meat bird will be "skinny". They should be skinny. Their breast should be a V, not a flat U like store birds in the meat section. If they are moving around, lively, eating, having fun, they are fine. If you can feel what is like a pencil on their breast bone and the sides are sunken in like a Y, then they are skinny and then you take action.
That said, some say you can eat eggs 10 days later, some say wait 30. Drop in production at this time of year is often normal. Less day light, moulting, aging, weather, all result in reduced egg production. Labels say never because they don't test it on chickens so to cover their bums, they say never. Some production breeds only lay well for the first year or so and then drop drastically. Perhaps they are hiding eggs too. If you suspect internal parasites, a fecal float test shouldn't be that expensive.
On "alternative" treatments. Some swear by them, some don't believe in them. I grew up on western and eastern medicine, and I believe western medicine is "safer" because it is tested again and again despite the few deaths per 100 thousand people the drugs have saved. I've found things like Mercury listed on things ingested in the eastern medicine, don't let anyone try to feed you snake gall bladder either, that stuff is disgusting.
I personally have not wormed my chickens ever and they do fine as far as I can tell.
