I looked into a lot of the people here who got sick on a plant-based diet because I switched to a more plant-based diet and it healed most of my health problems caused from years on a low-carb diet and when looking into their situations I found out that the reason most of them got sick was not because of their vegan diets per se, but because they simply under-ate on them. Under-eating long enough on any diet will get you sick.
What "AF" really is is malnutrition and that's why the symptoms of "AF" are EXACTLY the same as symptoms of prolonged under-eating/starvation and it's why all those people you speak who were on plant-based diets at the time developed "AF". They simply under-ate.