I recently installed a new fixture on my kitchen sink, and the pressure has gotten increasingly worse. I can turn on the hot water full blast and I get a little more than a trickle, and then I can add the cold water full blast and there is absolutely no change (improvement in pressure). The temperature is affected, so I know I am getting water from both lines, but the pressure is not. Note: my house is 52 years old, but the original hot water lines have been replaced with copper. (Cold are still original galvanized) Any suggestions?