Yesterday I left a sprinkler going, on low, under the tree for my dogs, the chickens were in their well moistened coop. When I got home a whole army of starlings and grackles were having a party, and there was about an inch of standing water. I brought the dogs in and turned the chickens loose. Tonight I think I heard a chicken sneeze. I cleaned the pen, faster than the bleach & rinse sterilization job I did on their waterer, and when I refilled the water I added about 1/4 cup organic apple cider vinegar, solids and all to their 5 gal bucket. I gave them swiss chard for a treat. Actually I think I heard 3 sneezes from one hen who wouldn't let me catch her to look at her eyes and nose. During the hour I spent tidying up I heard no more sneezes. Should I worry? Gypsi.