Before you said white spots now it sounds like you're saying you can tell it's actually pitting. Are you sure it's pitting and not machining marks that could have been there when the gun was new? You'd be amazed at how many MLs don't have pristine barrels right out of the box. I once dropped a bore light down a whole rack in the store, every single Traditions, a lot of the CVAs, and even a couple of the Knight guns had visible machining marks in the bores. This was years ago so no T/C to try.

Question is, do the guns still shoot well? If so, don't worry. And if you never got rusty patches, again I would not worry.