I remembered reading about the voltage thing, but also about diet and HLLE. From http://www.wetwebmedia.com/hllefaqs.htm, I quote Steven Pro:
"More vegetable matter, Nori fed daily plus some sort of herbivore diet like Formula II from Ocean Nutrition. I am sure San Francisco Bay Brand has something familiar. I am just use to Ocean Nutrition foods. You may also want to soak some of their foods in Boyd's Vita-Chem and American Marine Selcon. Again, there maybe similar products."
Another possible contributor to this HLLE problem is feeding terrestrial vegetables like romaine lettuce -- at least, that is what I've read on WWM. You mentioned nori sheets, but perhaps there is a vitamin deficiency at work here. I'm highly interested in whether or not you can turn him around. I hope you can. ..Karl