do you know if these black "specks" are "soiling" or could they be "gasket" type rubber bits? If they are bits of rubber you may be losing some critical "sealing parts" of the pump assembly. Old rubber bits tend to dry out an crack, eventually they can fail. I would take a peek inside the service access panel to inspect the pump, fittings and plumbing for leaks. Better to catch a leak early then later after prolonged water damage can ruin sub flooring etc.