Odds are VERY good they are just improperly adjusted.
Many factory wheels come with the bearings too tight, the thinking being that they will "break in" (if you call that thinking).
Try loosening them up until there is a slight bit of play when they are off the bike; tightening the QR will take up that play and they will be perfect.
At worst you might have to repack them (I would anyhow, but that's 'cause I'm anal) but I seriously doubt the balls need to be replaced.
FWIW, I think the 550s are the most unappreciated bargain in cycling.
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Today, I believe my jurisdiction ends here...