Well there is stainless steel and then there is stainless steel. It all depends on the stainless content of the alloy. The cheap stainless steel will rust! I don't remember the numbers for it but #306 seems to come to mind different spec for each alloy. FYI.
Yup -- the type of stainless alloy will determine its resistance to rusting. This is the first I've heard of the screens rusting, so maybe its not rust, but some type of other contamination? Have you tried cleaning the screens to see if it comes off? Just a thought.
Maybe one of the assembly line workers put his cigar out on the screen .
Odds are it's 304 stainless. 304 is used a lot for boat railings because it's cheaper than the good stainless (316) and a lot softer. 304 stainless does rust, especially from salt water. You need to polish it with an appropriate wax at least once a year. Metall is a good cleaner/wax for stainless.
Whatever you do, don't clean the stainless with steel wool, unless you want to contaminate the stainless permanently. Then you'll see real rust.