Don't know what kind of finishes on the guns but try using Balistol for cleaning. It's great for everything: metalwork, stocks and leather also. It comes in spray cans and liquid as well. Must have been something that you cleaned or polished it with previously?
Did you have them out in a rain or very damp conditions, then sealed them inside the safe? You may have to disassemble them and remove the stocks from receivers and barrels to get at the hidden mold.
I think you may have a serious mold infestation inside the gun cabinet now and must clean it out with Lysol solution after removing the guns. Leave the door propped open for awhile to dry it out and watch closely. Place a fan inside and let it run till you're satisfied. I've been pretty happy with those silicone gun socks: inexpensive and prevent rust.
Jim
