Also-
Try very hard to keep your grip consistent (tight) throughout the shot. If you are shooting low, it is often a sign that you are (involuntarily) gripping loose until right before the hammer falls, and then tightening your grip up.
This involuntary "squeeze" as the trigger breaks will cause your shots to all go low.
I agree, I was shooting low with my Glock and was dead on with my 1911. I started squeezing the Glock harder and the shots came back on target.