I had high potassium when i came to the end of PD but it didnt make me weak. It usually makes your heart race , in fact that is the danger ..heart attack , not weakness. Sounds to me like you just had a rough day , did you need to get that extra kilo off? I know you've had issues in the past with fluid limits and gone in way over. It could be just your body was adjusting to a 'rough' session .