Maybe there is dust that the fan is blowing around?It's a large dog kennel, about 4ft by 2ft, in a wooden shed. I do have a fan near them, but not pointed directly at them. It's actually pointed at me, I sleep by them incase they need something during the night. Here's the place they'll be moved to. I have to use shavings again in the large one because the paper towels would be too expensive. I don't think theres anything in the air that could be irritating them, I try to avoid spraying things in the house. Can you recommend anything else that could help stop the sneezing and mucus?
Try turning if off for a day and see if the sneezing stops.
They should be sleeping at night...they shouldn't need anything.