OK, that could explain how FC went from 16 to 18.5 without adding bleach.
Can you shutdown SWCG without shutting down pump / filter? If yes, please do.
How's the water look, has the cloudy cleared? Running pump / filter 24/7? How's the filter pressure?
Please test FC, CC, and pH add bleach if FC is below 15 and get a FC reading at dusk so we can see how we're doing at dawn.