You can, either by how Bill described, or lapping it. You’ll have to sacrifice a couple bullets to do it but it works if you’re getting rings on the bullets. Chuck a bullet up in a drill with some fine lapping compound applied and go to town. If they’re too long and skinny and smashing into the top of the stem then the lapping method obviously won’t work.
If you can return the Whiddens I think that would be the best route and just get some Redding’s or Forster. I bought my last set of Whidden dies years ago.