With those numbers? I'm guessing you have an algae bloom that keeps coming back because you let your chlorine levels get too low...FC=1, CYA=40. I think it may be dead algae that then needs to be filtered out.

The only other thing it could be is a high metal content, but of some odd metal like magnesium, where the precipitate is whitish. It's not calcium, unless your calcium reading is wrong and it's much higher.

Carl