before changing disconnect look at compressor #2 running over rated amps. dirty condenser might not be the problem with compressor #1 running good head pressure. i would look for an overcharged circuit with compressor #2 because higher pressures equals higher amps. also low superheat on circuit #2 which means you are close to flooding back, another sign of an overcharge.
I would bet on this. And I'm not even a betting guy. The disconnect may be worn out now since the fuses have been replaced so many times. You will probably have to tighten the fuse holders now if that's even possible.