Toad Brakes

My newly acquired '91 Tracker has near new pads and shoes all the way
around. The front disks and rear drums are in great shape.

My problem is that the brakes are dragging for some reason. All the wheels
are hard to turn!

I loosened up the master cylinder and put a 3/8" flat washer behind each
mounting flange, then re tightened. Wheels are free spinning now but
brakes a little soft.

Is this an indication that I need a new master cylinder?

Thanks
bdub
76 Palm Beach