I've been re-reading my old post-crisis Superman comics and was wondering if the origin of Superman's electrical powers was ever explained. I always assumed it had something to do with his efforts to regain his powers following Final Night, but the robots in the Fortress of Solitude stopped recognizing his Kryptonian DNA before that (Superman #117). What was the source of the change and when was it explained.
P.S. Another less pressing question I've had is when did Lex Luthor deiscover he had cancer? What issue?