Hi, Mickey. Considering that you have galvanized steel pipe from 1926, it is probably a wonder that it has held up as long as it has. You possibly do have one place to check before replacing the pipes though. If you have a mixer valve (diverts the water to the tub or shower head, you might check this first. If the pressure is low to both the tub and the showerhead, you might check the hot and cold valves. It is possible that a piece of scale or rubber washer has broken lose and is blocking the end of a pipe.
If the pressure is low to both tub and shower and there is nothing ovbiously wrong with the valves, it is probably the pipes that are scaled up and will have to be replaced.