Hmmmm, if you are off by 1/2 an inch and try to square everything up to the smaller size you may be loosing points. Don't know what your blocks look like though. Might be ok. I would square up the worst one, then attach it with a quarter inch seam to scrap pieces of fabric on all 4 sides to make sure you are not loosing some of your design. Use a long stitch length and just unpick the stitches after the trial joining. This will let you see if it will be OK to proceed with the rest of the blocks!