why are they allowed feed near their bedding? (or have I misunderstood?~)
Grains can fall inbetween the bedding and and get moldy and suck up moisture encouraging mycotoxin which can screw up their system in small quantities. Sometimes with younger birds they are simply curious. Giving them a small treat of their favorite )yogurt or now that it is cooler a wee bit of scratch) before they go in the coop at nite will usually take care of that problem.