Monk's Powerful Fist says
When striking with your fist, you deal 1d6 damage instead of 1d4. You use your
normal proficiency when making a lethal attack with a nonlethal unarmed attack
It specifically makes note of you "when striking with your fist" instead of something like "When making an unarmed strike".
At the same time, later on it talks about lethal and nonlethal unarmed strikes
So do my kicks also have the ability to be lethal, like my fists, but only do 1d4?