Hits that are down and to the left are pretty common with striker-fired pistols, and this afflicts a lot of new shooters as well as more experienced shooters who get in a hurry. It is related to pushing the gun to the left a bit - presumably by tightening the fingers - at the end of the trigger squeeze (for right handed shooters). If you look at your grip, and simulate a trigger squeeze (without the pistol in your hand), you can see the trigger finger moves to the left the further it goes, because of the geometry of the fingers. The other fingers move sympathetically to the left with the trigger finger, too -- pushing the pistol in that direction.
Probably better to work on the trigger stroke before altering the position of the front or rear sight on the slide. I struggled with this a long time, with several different pistols, but it has gotten better with practice.
