We have 5 bathrooms in our home. In one bathroom the water comes out with hardly any force in one sink. We changed the faucet and the supply lines under the sink. The problem has continued. A second sink in the same bathroom is fine. However, the shower in this bathroom seems to be starting to have pressure problems as well. Any ideas?

Check angle stops. They may be corroded and blocked. Also, try to run water in the subject sink w/o aerator. See how much water flow you get.