Over the course of a few days, my flock has gotten sneezy all of the sudden. I thought it was the temperature change as things start to cool off, or maybe some plant that's flowering. Now, all of the chickens occasionally break out into fits of sneezing–some more than others–and the 12-week-olds seem to be the most sneezy and snotty, one of which is wheezing. I was told that garlic in the water can help their immune system, and that cleaning the coop and diffusing it with gentle essential oils might help, but what else can I do, and what might this sickness be? Any help regarding this would be much appreciated!