Okay I think you have several things going on here. First, when you iron your segments, make sure you are moving the iron in an up-and-down motion, and not wiping the iron across the fabric, which will stretch the bias. Second, I think you need to square up your hourglass segments before sewing them into the block. That one in the center left is way too tall. The hourglass segments should be the same size as the reddish fabric you're using in the corners.