Hmmm.....let me think. Probably most of them are a mix between silkies and RIR's. And DH had traded some baby chicks at the feed store, for a baby duck and three baby guineas. Maybe the guineas are the culprits?
I suppose some will generate dust, even though they have only been in a breeder and never outside? The only difference in the Feb. group from our two other groups, is the guineas.