More info needed.
Do you twist at all during the movement? How do you do your db rows? Bent over? seated? with one foot on the bench?
Maybe this relates to your discomfort -- I just plain can't do bent-over bb rows because they hurt my low back (I injured myself as a kid). Something about bending over with all that weight at the other end of my torso - I threw my back out for a week doing them. So now, I stick with Yates rows (more upright position).