Yes..it is suspicious, it's not cloudy enough to capture it with the camera, like I said the carbon reactor has cleaned it up. I may never have an answer. All I can do is a water change and hope for the best...I wish my RO would work faster.Color looks fine so not sure what it could be. Your large water change seems like the best option and checking for unusual stuff like stray voltage, rusty magnets, air fresheners that may have floated into water, etc...
I still keep thinking about the cloudy water though and seems really odd as a telltale sign because you started losing fish at the same time.