It's not uncommon for this to happen when a mature fish has the conditions it is kept in change dramatically. All you can do now is wait and see. Is there another fish hanging around this one? I've seen both female lay eggs alone and two females lay eggs together and afcourse what we all want a pair male/female pair. Only way to know for sure is if the eggs hatch. Just watch them. three things can happen: 1) they remain clear and hatch. 2) they turn white. 3) they get eaten.