I drained and refilled my Optima, due to a FLO error, which included replacing the filter. When I started it up, it would not come on. Serviceman determined bad circulation pump, so I had to drain the spa again and wait 2.5 wks for him to return. He replaced the pump, and when I refilled and started the spa, lots of whitish, flakey gunk blew out of the jets. Spa Store advised it was "water mold?" and to put in 1/2 bag of pool shock and circulate for 1 hr., then drain and refill, which I did. At startup, even more gunk blew out of the jets. I have used a skimmer to capture as much as I can, but feel like there is something else going on. Any ideas on how to resolve?