just got the o'le girl out for spring. checked fluids and found the rear resevior very low. added fluid. fired her up. pulled out of the barn. "mushy" pedal. she stopped, but pedal almost to floor. no issues prior to today. the pedal gets firmer with consecutive pumps. rechecked res. levels. rear res. looks down mimimally. had the queen come out and pump the brakes. can't see any leaks. rear res. level holding steady. have any of you experienced this? does the system need bled? all suggestions welcome.