Take it to the lady with the JoolTool.......
Just kidding!
As many TRFers have already mentioned here, SUS doesn't rust. There are exceptions, but the steel used in wristwatch manufacture has a low carbon content which resists oxidisation, even in harsh environments. If the "rust" you talk about had only been on one side of the bracelet, then I would've been inclined to suggest that you have picked up some carbon steel (mild steel) from somewhere and cross contaminated your bracelet. But because it's appeared on both sides, that would suggest a defect in manufacture, welding process, material, etc.
Perhaps the best answer would be to return to PP, for a full explanation and replacement bracelet.