Rust on stainless steel cables

Do you have recommendations on how to keep the cables under the bottom bracket dry? A couple of mine are rusty now which is surprising since I thought they were stainless cables.

The cables are stainless, but depending on the nickel content, “stainless steel” is still susceptable to rust.

The best defense is to apply a lube like Tri-Flo into the cable housings. By arranging the control to provide some slack in the cable, you can unstop the housing from its frame braze-on and slide the housing up the bare cable to expose the cable normally inside the housing. This makes it easier to apply the lube.