Hi and welcome! I sense some frustration here! We'll help you get this figured out!
You really need your own testkit so you don't have to depend on the pool store. You can get a good kit which will save you a lot of money in the long run. We recommend either the Taylor K-2006 or the 2006C which has larger quantities of reagents. With a pool that has a high chlorine demand like yours seems to, you should probably think about the 2006C.
Dichlor has CYA in it and that may be why you have the increase, although a 33 ppm change since Sunday doesn't seem likely. Most likely tester error.
How often are you adding chlorine? To get this pool clear, you are going to need to test and add chlorine a minimum of 2 times a day - early morning and evening after the sun is off the pool. But, actually it will clear faster if you will test and add chlorine as many times a day as you possibly can.
I would suggest just using bleach as your source of chlorine. You don't want any more dichlor shock or even trichlor tabs because both of those will raise your cya level even further, which you do NOT want. I wouldn't use cal-hypo because your hardness level is already at 400. Bleach will not raise anything except the chlorine level which is what you need. In a 21K gallon pool, each gallon (4-qts.) of 6% bleach will raise your chlorine level by about 3ppm.
What you need to do is test as often each day as you can and each time, add enough bleach to raise the cl level back up to 20ppm. You want to try and sustain this high level and not let it yo-yo up and down. If you will do this consistently, it will clear your pool. It may take a few days. When you get to the point where you are not losing more than 1ppm of chlorine from sundown to sunup then you can let the cl level drift down and then keep it between 5-10 ALL the time. If you let it dip lower than 5, you risk another algae bloom.
Also, run your pump 24/7 right now.
Watch your pH. You never want it lower than 7.0 or it becomes acidic and will damage your pool. If it drops, add some 20 Mule Team Borax (in the laundry aisle at Walmart).
Hope this helps. Repost if you have further questions.
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