It's not so much that lack of potassium causes stones. It's more that citric acid itself has an effect vs. metabolic acidosis.

https://kidneystones.uchicago.edu/h...into-the-urine/

Whether you should actually take potassium citrate and how much is a bit above my pay grade. I'm just pointing out one situation where some degree of metabolic acidosis with a ketogenic diet might result in kidney stones.

It's really impossible to connect the stones to the diet for certain unless you know for a fact that you weren't already developing kidney stones before. You have a correlation for the symptoms, that doesn't tell you when the stones started forming.