Found one of my Hens dead today. It had a yellow like residue attached to the underside of its feathers in a few spotsl The residue would just crumble in my fingers when I touched it. We had alot of rain today and the flock was free ranging so its possible that the residue was soft and crumbly because it was rain soaked. Any thoughts on what this is and if it could have caused the death. Hen was about 1.5 yrs old and seemed to be healthy. No signs of struggle or predator attack. Thanks for any help.