Well, does Marineengine have another set to exchange them for?  If so, perhaps they can have a look at the replacement set.

If not, perhaps they will offer a partial refund.

I wouldn’t be to concerned about that minor rust, unless you feel there may be rust preventing the reeds from sealing completely.

I would just use the WD40 on them, or perhaps some OMC engine tuner, just be sure to spray them with oil afterwards.  You could dismantle the reeds and clean them with some scotch brite pads, but you need to be very careful to reinstall them exactly how they were to begin with, don’t flip them over.