Performed 9 system cooling maintenance. System 1 starting from the back side of the building and working toward the front. Marked supply plenum with a number as a reference. Black mold growing in system 1 supply plenum. Recommend u/v lighting installed to kill mold and bacteria. System three has no secondary water switch. Because system is horizontal if the evaporator pan were to ever become clogged they could run into the plenums and miss the pan completely. Recommend installing in line PVC switch to avoid this. System 5 run capacitor will need to be replaced by next visit. System 6 that supplies front of building has black mold growth in supply plenum. Recommend installing u/v lighting for this supply as well. Recommend hard start kits for the 4 older outdoor units. This will lower amp drawl and unit noise while prolonging life of compressor. All units operating properly at this time. Refrigerant levels are acceptable on all units. Changed all filters. Cleared all drain lines. Teste