Give it a trip or 2 more, and if you continue to shoot a little lower, put the #3 sight on. I didn't have to do that with either of my Walthers, but I did have to do it w/ my SW99. It also kinda depends on the ammo U use (weight and brand). I typically use either WWB or CCI Blazer 115gr.
Also, I "cover" the center of the target w/ the front sight dot. If U use the top of the target and put it at the bottom of the center, that could explain it.
Try this, dry fire practice at the range. Squeeze trigger then leave the gun on target (sights aligned) for a slow three count before moving to the next trigger squeeze. Kinda like follow through on a basketball shot or golf swing.