Water pressure became a problem - city water
You may have galvanized water piping in the house or between the street and the house.  Over time these pipes corrode and the corrosion and collection of minerals makes the inside diameter of the pipes much smaller.  This restricts the flow of water and would explain your issue.  Sadly there is no good fix beyond having the piping replaced with modern copper or plastic.  See this article, note the 5th paragraph describes your issue with the shower and washer exactly.