If there are only a few blocks that are too small I'll see if they can be taken apart and resewn, since sometimes it's just one or two seams that are off. I also sometimes just make new blocks to replace the ones that are too small.
If there are a lot that are too small, I would cut them all down to the smaller size. It's time consuming, but I don't think I could ease in that much without a struggle. Since there are so many blocks, maybe cut down the biggest ones and ease in the rest?
Squaring up blocks is a good time to listen to radio shows, podcasts or audio books!