a fowl smell

[gene]

I received a bunch of down/feather pillow inserts from a customer. Many of them smell like rotten eggs / sulfur, when I open the bags. I like to put the inserts in my pillow cover, then into a plastic bag, and be done with it.

I had these sitting out for a few days and the smell is now very faint.

Anyone know what might cause this foul fowl smell? I'm wondering if it's in the cleaning process or did something microbial grow after they were plucked and cleaned?

gene