I think that the male has decided to be more dominant, and is trying to become the female. If the larger clownfish is truly a female (already gone though the sex-change) than this is not possible. BUT if both clownfish aren't fully mature yet, the previously-thought male may become female.
90 Gallon Reef - 3 Blue-Green Chromis, 2 Ocellaris Clowns, 1 Kole Tang, 1 Midas Blenny, 1 Longnose Hawkfish, 1 Zebra Dartfish, 1 Algae Blenny, 1 Six-Line Wrasse
29 Biocube Reef - 1 Chalk Bass, 2 Black and White Clownfish, 1 Yellow Watchman Goby, 1 Fire Goby