I often see this activity when a tank of young adults are raised together. Typically, the females twitch, dance, even make dry spawning runs. Females will often go through this activity together, while males watch. You also get times when young male + female will clean a surface and go through dry spawning runs. Unfortunately, its not a prelude to spawning. They may not spawn for another 4 - 5 months.
Have patience and don't be dissappointed if nothing else happens. Something will eventually.
Willie