Converted ID3 tags, now iTunes can't find album art (but QS can)

So recently I read that Quicksilver doesn't display embedded album art for some tracks if the have older ID3 tags, so I converted my whole library to 2.4. However, a few songs seem to have lost their album art along the way. The thing is, Quicksilver does display album art for those tracks, so clearly it's still in there somewhere, but iTunes doesn't seem able to find any at all. Any idea how I could get them to show up in iTunes again??