So today my hen Lemon has been wheezing. She sounds exactly like the chicken in this video. She was fine yesterday, none of the other birds are affected, and I haven't added any new birds to my flock recently. I did add some leghorns a few weeks ago, but they were quarantined first and show no signs of illness. My friend also took birds from the same flock I got my leghorns from, quarantined, and introduced them to her flock and all are healthy, so I doubt that the leghorns brought anything with them. She has no other symptoms, no sneezing, no eye discharge, no nasal discharge, no smell, droppings are normal, she ate a little while I was out watching her - just not sure what it could be.