If the lube's not visible on the blades then it's most likely on the blade operating ring or the housing for it.
This is the ring that the aperture blades are connected to. Waaay down deep in the nether regions of Hades. I mean your lens.
Well, John, if that is the problem, then maybe we need some Bardahl to take care of that "Dirty Sludge, Sticky Valves, Gummy Rings, and Blackie Carbon!"
Ralph Javins, Latte Land, Washington
When they ask you; "How many Mega Pixels you got in your camera?"
just tell them; "I use activated silver bromide crystals tor my image storage media."