I'm sorry to hear this.Maybe it could be some kind of a bacterial infection and this is why some of your cats don't have it. My Sky had something similar to this and I thought for sure it an URI but none of my other cats got sick. I hope that it's nothing serious and that they get better and feel better quickly.
I painted most of my condo last year and none of my cats had this sneezing problem so maybe your cats are more sensitive to the smell of paint.
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