Since the blocks are crocheted I agree that working a row of sc around the smaller blocks to even out the sizes might work better. If you've used synthetic fiber yarn, when it is washed and dried the blocks will all want to return to their original size.
Cheating is an option. . . . Cheaters never win and winners never cheat, but smart knitters who want to retain an iota of sanity do, cheerfully. ~~Kory Stamper