Probably happened back east in the high humidity zone.
One would think a Vet's org would have at least cleaned them up a bit if there was some sort of a weather event that got them all wet.
I had to be extra careful with my stuff when I was stationed in MN due to the humidity. Used these and the Brownells equivalents.
VCI Gun Bags made from PE film embedded with Volatile Corrosion Inhibitors that form a protective barrier for metal protection. Simple place the item in the bag. No cleaning or degreasing required after unpacking.
shop.vciandlubricants.com
I even take those precautions here even though we're a lot drier.