It's important to mention the details of your social dynamic to both the shy and boisterous individuals who may seem like they aren't concerned with its fluctuating composition. For if no one ever mentions anything to them, they may start trying to deduce what's happening based solely upon body language and innuendo. You can learn a lot from doing this but nothing's ever certain, and mistakes, though rare, are often made. Mentioning actual truthful details may save them some trouble, especially if this goes on for years and the grip separating hypothesis from fact slips away.