another suggestion to explore? A friend's child was recently diagnosed with potato intolerance. I thought this was very unlikly and probably a sign that they'd wasted money on a quack. So I googled and came up with this report (from a reputable allergist) talking about the effect of potato intolerance on behaviour.
www.allergiesexplained.com/20-Potato-and-other-foods-can-cause-eczema.htm