Oh. Thank you!you have to make them horny/devoted/excited. One of the girls has not had their "normal" state changed to one of the states mentioned.
This is usually most easily done by using the preferred action on them until the 3 bars under the associated stat are maxed. then cycle the time and their mood will change.
Since you already have 9 of them, I am guessing you probably already know how to do this.