Maybe when you pressed the fabric there was a little sticking instead of slipping due to the starch and it got out of shape. I use a plain flat iron which doesn't steam, no starch, and a gentle spritz of water. I only starch when wrinkles won't come out any other way, or I am stuck with prewashed fabric that needs major resizing. But I don't prewash (ooooh get the quilt police!!! LOL)