I have a new 2021 TAB 320S with a stainless steel sink...I think. I've had it for a month or so and used the sink periodically without a problem. However the other night (in my driveway) I ran some water through the sink from my fresh water tank. I had filled the tank a few weeks ago with filtered water from my house. Today, after the TAB had been closed up for a few days, I went inside to see rust stains all over the sink. Some areas were quite deep and starting to pit! I know that some lower grade and martensitic stainless steels will rust....but I was really suprised to see this. Has anyone had a similar issue? I read on line that I might need to get an iron filter for my water source, but I've never had significant rust stains anywhere else. Any help would be appreciated.