I saw the post but the subject matter was way out of my league. Best not to respond in no pertinent advice can be given. That said, taking on extra responsibility with a special needs child should engender better remuneration. You do not want to find Star asking for a "Talk" which might involve her saying the work load is increasing but the money is staying the same. Show you value here and make it worth her while.
@Gusman I love Star like a daughter. So I would never try and take advantage of her. I give her free room and board and pay her 50$ a morning to get my kids ready. Days there is no school she gets 150. Summer break she gets 700 a week. I am not opposed to paying her more to care for Joels son.