On arrival downstairs unit producing 17 degrees of cooling while upstairs only produced 11. Upstairs unit has bacterial growth in coil area, downstairs is clean and in good condition. Outdoor units passed all electrical testing. Found upstairs unit with a 1.5 subcool and a 40 superheat, verifying that the system is low on refridgerant. The evaporator coil while running is around 32 degrees and is likely to freeze up with continued use. Advised customer and she will pass info along to husband.