[karmicthreat]

My guess would be barring some metallurgical mistakes the stainless surface is getting contaminated during production. We do a decent chunk of stainless steel production where I work and we keep any tools that might be contaminated away from the stainless production. We also bead blast the surface and passivate it to keep it contamination-free. Just any little bits of non-stainless metal will corrode and permanently stain the surface.

[eyegor]

Eh, it's uncoated low chrome stainless (some 300 blend). It wouldn't take much to start surface rust. In my experience low chrome stainless will rust in months if it hangs out too close to normal steel (some kind of galvanic migration?). Since they just started delivery and it's winter, you'll know for sure (by spring) whether it was contamination or if they're all doomed. Road salt is much worse than salty air.

[theGeatZhopa]

It's called s local element, where two different metals are having reaction with each other with one reducing the other chemicaly. You also could reduce it by having a sacrificial anode metal like on ships which are all the time in the water :)