I performed full system evaluation on two systems and inspection. The Downstairs system: Found system low on refrigerant this indicates there is a leak inside the closed system losing the refrigerant. I Recommend having a leak search performed to locate the leak. I also found mildew growth on evaporator coil casing and supply plenum. I recommend having mildew growth removed, supply plenum replace and installation of a uv light to kill bacteria. I tested delta T / Temperature split the supply air 59.2, the return air 70.4 the split across coil is 11.2 the system calls for 18-20 degrees split across coil, this indicates system is undercharged and not performing to manufacturer's specs, Also indicates there is a leak or restriction in the closed system. Tested Furnace and operations found no issues at this time of inspection. The Upstairs system: I discovered weak start capacitor on condenser unit, Recommend having it replaced to not cause damage to the system. Tested refrigerant p