If this is your first attempt at machine quilting you might want to view some videos on getting the sandwich ready. I am going to assume you basted the sandwich with spray basting, pin basting or thread basting? This keeps the layers from shifting as you move the sandwich around. Are you using a walking foot for quilting straight lines? It helps prevent puckers on the back. You could stitch diagonal lines from corner to corner of each block through the whole quilt. This will stabilized the quilt and will set you up to do spiderwebs in the plain blocks. The plain blocks will now have the two lines in it like a large X. Add the horizontal and verticul lines to the plain block and you have the frame for the spiderweb ready. Quilt in the web lines using the spiderweb frame.