1. Stop adding ANYTHING but bleach.

2. Stop going to that pool store; neither their testing nor their recommendations are trustworthy. Remember, THEIR ADVICE put you in this situation. And without going into the technicalities, I can tell simply by looking at the numbers that their testing is bogus. Remember, pools stores make money when they sell chemicals, NOT when they solve problems. If they actually solved your problem, they'd sell less chemicals!

3. Go to Walmart or equivalent and get more STORE brand 8% bleach. Clorox from Sams is OK, since they only sell plain bleach (I think), but Walmart sells 'flavored' Clorox, which you do NOT want!

4. While at Walmart get a cheap OTO/phenol red drops test kit. Use it when you get home, and report results.

5. Order a K2006 kit ASAP -- try to get one from Amazon, if they have them. If not pick Amato Ind as a 3rd party seller. The 2 oz size is a better deal (K2006C). http://pool9.net/testkits

6. Really. Do NOT put any chemicals in, except bleach. Keep adding doses till you get a dark yellow OTO result.

7. Do NOT get a "compares to" cartridge: the way they 'compare' not a good way! Get a Unicel, Filbur or Hayward OEM, when you replace, and make SURE the cartridge itself is labeled Unicel, Filbur or Hayward! I don't know if you need a new cartridge, but here are Amazon links:

Cartridges for a Hayward CX1900RE
Unicel C-8420 Replacement Filter
Filbur FC-1211 Antimicrobial Replacement Filter Cartridge