Oy
If that is indeed corrosion,it is entirely possible that someone ran a batch with the wrong type of metal; it wouldn't be the first time it has happened. Of course, it is also possible that there is something else in there that is corroding, but it is hard to imagine what...
In any event, your mandatory next step is to disassemble the fitting and taking a good look at the wedge. If it isn't stainless, it should be obvious by now.
Fair leads,
Brion Toss
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