First I would iron all my blocks and make sure that they are laying flat with no tucks. Then measure all of your blocks. Choose the block size that you have the most of. Then work with the other blocks to see what can be done to get them to that size. As suggested it might mean using thinner piecing thread. It might mean sewing a smaller seam or a larger seam. When you quilt the quilt use an overall pattern that goes over the seams to stablize them.