A few times recently, I've pushed the brake pedal and I felt like it was spongier than normal and travel was increased. Letting go and pressing the pedal a second time yielded a normally hard pedal. Fluid level in both ends of the tank is full. No leakage at the wheel cylinders is evident.

Am I correct that this seems like a master cylinder sealing issue and that replacing or re-sealing the MC should solve it? Or could air be getting into the system at the wheel cylinders without fluid out?

Getting this looked at by a mechanic tomorrow. Between this and the alt issues, the car seems a bit jinxed