yep, fabric shrinks. If I buy a kit from a quilt shop I generally do not pre-wash as sometimes, they give just enough before you wash it as you have discovered. I also have bought kits that have fat quarters which actually are not fat quarters and I have been unable to cut out my pieces with them. I have substituted fabric from my own stash if I have something that will work. Also some 10 inch squares and jelly rolls end up not being the full size they claim to be. I generally do not buy kits often but will on occasion.