I hadn’t thought of the dust bath material leaving via their feathers, but that makes sense. It’s amazing how much dirt they load up in their feathers!If they're all active and healthy I wouldn't worry about it. Dust bath substrate always vanishes quickly even if they're not picking at it, as they'll get up with it caked in their feathers and then shake it off all over the place, effectively emptying the spot of whatever material was in it.
(The Buff Orp is Very Into dust/dirt baths
