DWM;

If you were my local customer, and I was visiting, I would say "Hm-m-mh, let me take a look." and then proceed to verify everything you've told me. I can't do that.

So let me suggest that YOU do what I'd do next, if I were there.

I'd disconnect 100% of your SWCG and feed system (and make 100% sure you couldn't turn it back on behind my back -- been there, got blamed for the "inexplicable" problems, NO thanks), and then have you run with bleach for 2 weeks, and see what happens.

ALSO . . . I'd test your water, and especially your TA / CA with my OWN Taylor based kit. And THEN, I'd test your fill water.

But, since I'm not there, I can't do that. But it's what I recommend to you. You'll need a Taylor K2006 -- Amazon links in my signature.