RX8Club.com - Master cylinder problems?

So I have a problem with the master cylinder…I think? I have read a lot of threads on master cylinders, clutch brackets, etc… The story goes everything was fine I was checking all the fluids one day and seen the brake reservoir needed some fluid, so I got some dot 4 put about a ¼ of an inch in the reservoir. Then it seemed like a few days later the pedal started sticking on the way back up. It has got increasingly worse since. Now the clutch pedal won’t come back up at all. I am thinking it’s the master cylinder, but I don’t know if the dot 4 would have anything to do with eating seals or anything like that? If not am I way far off line thinking it’s the master cylinder? It goes into gear fine, comes out of gear fine, and drives fine; the clutch pedal just stays on the floor now. And one more thing if I have to replace the master cylinder can I bleed the line at the slave cylinder only or do I have to bleed the brakes as well since it is all connected? Thanks for any help.