I think 7mm Woodsman hit the nail on the head. You might have a condition with your skin where you have a ph that is slightly acidic and moist. If not, then be aware of where you're storing your guns. I prefer to use dessicant like calcium chloride in the closet where I store my treasures. Also, use a slight constant breeze from a small fan to keep the air moving. The RemOil w/ teflon works well as does my favorite.....good ole Vasoline! For short-term storage I really like to use Ballistol spray (absorbs the water) and a silicone treated storage sock.
Now, if you do see signs of Fe2O3 (rust) get out the 0000 steelwool and the RemOil and start rubbing it out ASAP!
Jim