If potatoes help you, you may have/have had potassium/phosphate deficiency among all.
You are asking if I experienced def. related to fasts - no, but all is different for different ppl. I've experienced def. outside of fasting. Fasting isn't what brought them up to you. What brought them up was your conventional lifestyle before the fast. Also the fast isn't going to make you def., but if you don't take care to replenish and compensate for decades of sub-optimal feeding, the fast isn't going to replenish lacks of minerals or vitamins either. It has to be fasting followed by replenishing.