I have 4 outlets in one of my bedrooms. One of the outlets is working with no problem at all both the top and bottom plug work. The other three outlets in the bedroom, the top outlet works but there is no power going to the bottom outlet. This has occurred on all 3 separate outlets. What could be the cause of this, should I be concerned. I tried resetting the breaker just in case, but that did not work. Thanks in advance