I put acv in the water or a tiny splash of bleach or vitamins. Whatever it seems like they need. I mostly bleach in the summer when the heat grows bacteria like crazy. I also put diatomaceous earth in their regular feed. Once a week, I let their feeder run out and when they are hungry, they will eat rooster booster chicken vitamin pellets. They are the shiniest feathered, hardest shell laying hens I've seen. Oh and they get lots of high protein meal worms as treats. It's like chicken crack!
I think the acv helps them metabolize the oyster shell calcium too. Anyway, my rambling point is to do what works for your birds in your situation on any given day. You'll see a lot of tips here. Try them till you find the formula that makes your birds healthy and happy. I vote YES to ACV. Definitely worth a try