If they were just wearing out, it would be hard to get any tension at all. You are getting too much which, to me, would mean it's either dirty and sticky or the tension release mechanism is not working correctly.
On the back side of the tension assembly is "little doohickey" that engages the tension once the presser foot is lowered. Look inside the "nose" of the machine and raise the presser foot and watch what happens (the mechanism should go in and out as you raise and lower the presser foot). If it isn't moving, put a drop of oil on it and raise and lower the presser foot until it moves back and forth freely. If that is the problem, you will notice a change immediately.
Usually, cleaning the disks solves lots of problems. Just use a metal polish. I usually use Brasso, which works well. There may be better products. I don't know.
If you decide it needs cleaning, be careful to take photos of it as you take it apart. The photos should include which direction each piece is faced. Getting them out of order or one turned the wrong way and the tension won't work, which Joe suggested might be the problem.
bkay