Power fluctuates enough to make bedroom fan almost turn off
That's a power supply problem, and a serious one.  If it is happening all over the house, and if any appliances will cause it, then it's a "lost neutral" -most likely on the power company's side of the meter.   That is their problem and they should fix it for free.   Call them and report an outage, since it is as serious as an outage.  Don't delay, either - this should be fixed right away before it does serious damage,