It's a low end group.

4 years ago when I had a community shop build me a touring frame to commute on we tried to keep the budget under $400. We ordered new shimano wheels with mavic rims and galvanized spokes. What a joke those pieces of crap were. I'm still running the front with 90% seized nipples and nothing remaining of the original hub but the shell, seriously, I have even replaced the cups. The rear only maintains the shell and original cups the wheel having been relaced after the rim failed. Anyway they still make wheels with garbage spokes. I wouldn't bother cleaning and I wouldn't bother relacing. Spray the nipples inside and out with liquid wrench and let them sit for a day then true them and ride them.