Waterbear,
Ah, that makes sense! Thank you for explaining that; I had no idea the two were related. And I bet you're right about the tabs (pucks), too.

Ok, I retested everything this morning... no real surprises:
FC = ZERO
TC = < 0.5
pH = 7.4
TA = 100
CYA = 50 ??? Is it normal to drop that much in 2 days??? It was 65 on Sunday!
CH = 370

Ok, so I added 5 more gallons of bleach early this morning (right after testing). It's kind of overcast here this morning so hopefully it will have some time to work before the sun hits it... I was afraid to let it sit all day in the heat without adding at least SOME chlorine!
Going to the store to buy MORE BLEACH today!!

Side Note: It *appears* as though the stains are GONE so maybe *something* worked (or all of it). I realize they could come back as I continue to bring my chlorine up, but I just wanted to note that now...
I'll check in again later,