Is anyone else having trouble with canning lids these days? I'm finding that my pickles and tomatoes (anything canned with vinegar) are not maintaining a good seal much longer than a couple months! The lids start out sealed perfectly, but later on they just come right off with no effort....then I see that there is a little black speck on the underside of the lid and sure enough, a tiny pinhole where the metal lid was eaten through. This used to never happen! I use name-brand new lids (Kerr, Ball) but it seems the quality is different now...anybody else encountering the same problem? Any suggestions what to do??