غَفَلَ describes becoming heedless or unaware; it does not mean striking someone.
ضَرَبَ names the act of striking.
ظَلَمَ describes acting unjustly or wronging someone. It is not simply another word for every act of striking.
The forms غَفَلَتْ, ضَرَبْتُ, and ظَلَمُوا keep these basic meanings while their endings change the doer.