I have astigmatism in my right eye which cause all my shots to be on the left (compared to most other shooters).
Adjustable sight solve that problem.
I also use international shooting glasses for serious target shooting which allows for my lens to be 90° to the target, so no parallax.
Different commercial ammo and reloads will have also cause different impacts.
Check the lot numbers if you tend to buy the same brand and model of ammo.