Take that piece out and try a regular piece of fabric to see if it is the machine or the bulk of the fabric causing the tiny stitches. If it is the machine it is possible that the bobbin is hanging up somhow. I have to ask, did you put the foot down while changing the tension? If you didn't, it didn't change a thing. It has to be down to change it.
Also, check the way the thread is being held all along the line of the machine. Sometimes it accidently gets stuck somewhere, or the tension disks need cleaning with apiece of dental floss. All else failing the machine is just not happy with the density of the quilt. Oh one more thing... open up the machine and clean out any threads hanging around that don't belong there.