Lisa of Fresh Eggs Daily swears by garlic cloves in the water and powdered garlic sprinkled on the feed, in a mix of other supplements. I've never done it in the water, and did try the powder for a year in the mix. I've not gotten back to it, as it was pricy to do. But the chicks and broilers and hens did very well that year.

Garlic is anti fungal, etc and with all the problems showing up, it might be worth a try.