My son just started doing nasal washes. Did the salt mixture wreck my brushed nickle faucet?

I’m in process of cleaning our master bathroom and to my chagrin there are ingrained dark splotches all over one of the sink faucets. I can tell that I won’t be able to get this out.

I am racking my mind trying to figure out just what happened as they were fine a couple of weeks ago. I’m aggravated that the faucet (which was really expensive) is now permanently wrecked.

Could it have been the salt solution that he uses for nasal washes?