38 year old Price Pfister fixtures with three handles (hot, cold and shower diverter). Water was leaking from the handles of all three. We changed all of the washers but now the water pressure from the tub fill spout is extremely low. However, the shower has full pressure. Should we have changed out the entire stem cartridge rather than clean them and replace the washers? Will replacing the cartridge restore the water pressure? Also the knobs feel "tight" - meaning they are more difficult to turn.