Flip top leaking bad

Now that you say that.... I made a run home for lunch and was driving...aggressively, and by the time I made it home ( 5 miles ) the front part of the reservoir was dripping and was almost empty ( reservoir for the rear brakes ). Could a stuck proportioning valve cause too much pressure?
I'm half tempted to put a huge hose clamp around the thing to see if it's really blowing out.

This may or may not be related but I've also noticed that the front rotors get a little blued/black when driving hard