Clutch Problem: Getting air in line over time

I replaced the mc and slave cylinder about 5,000 miles ago. All has been well until last week. I started losing clutch pedal. I checked all of my connections for tightness and gravity bled the slave. I don't see any fluid leaks anywhere. All returned to normal with full pedal. Here I am about a week later and losing pedal again.

Anyone had this problem before?

 

Sounds like its drawing air in around one of the pistons. I've seen it happen on slave cylinders.

 

Bought a new slave at lunch today. Gonna try it tonite. Last one I got was a cheap one from Rock Auto.