Clutch problems on 1997 Tacoma

1997 Toyota Tacoma, 3.4L V6, 4WD, 135K miles. New clutch installed by dealer appx 14 months ago at 115K miles.
Around 3 months ago the clutch pedal began to not come all the way back up when you released it. It got progressively worse. I changed out the slave cylinder. This seemed to make it better for a couple of days, then the problem returned so I changed out the master cylinder. This appeared to fix the problem until a week ago. Now the clutch is not fully disengaging from the pressure plate when it is pushed in. I can't fiind a leak and the fluid level doesn't appear to be changing. Bleeding does not seem to help. Both the slave and master cylinders I installed were after market parts. Any idea how I can track the problem down and fix it for good?
Thanks