My Clutch is being weird!

Fountainhead

Ah, if your fluid level is not low, and you have weak pedal it's the Master Cylinder, NOT the Slave cylinder. CSC always, always, fail the same way, they lose seal on the O-Rings, and the pedal never comes back. Then the fluid reservoir for the clutch empties because every time you press the pedal, if the CSC is leaking, you're squirting fluid out of the CSC.
Of course your fluid could have gotten hot and boiled a bit, but usually that's indicative of dirty fluid needing cycling/cleaning out.