I searched this forum, but could not find any thread to help me...

My in-ground, 15,000 gallon (16’x32’, 3-6’ deep), plaster/gunite pool was completed Sunday, May 21st. They filled it and a guy came out on Tuesday evening, May 23rd, to start the filter, add the chemicals and show me how to maintain the pool.
After he added a bunch of chemicals, the chlorine level was at least 3.0. (I have a Pentair 5-in-1 test kit that tests for chlorine/bromine, Ph, acid demand, and total alkalinity.)
The pH was about 7.6-7.8.

On Wednesday evening, I tested the chlorine and it was non-existent. The test kit showed the sample as totally clear, no yellowing. The pH was at least 8.0, if not more.
I wasn’t able to get any chlorine tablets (I have a Pentair Rainbow 320 Chlorinator) or Muriatic acid until Thursday evening. After adding the chlorine tablets and 3 pints of acid, the chlorine level was still non-existent and the pH was still at or above 8.0.

I re-tested Friday morning and the chlorine is now existent, maybe 0.3 (it’s slightly higher if I get water near one of the jets). The pH is still at or above 8.0.

The water is also slightly cloudy. I can see the white filters at the bottom of the deep end, but not clearly. I’ve been brushing the plaster daily, does brushing cause it to be cloudy?

Is all of this normal for a new pool? Will it take a few days or weeks to get the chlorine/pH levels where they need to be?

PS: I would like to follow the Hamilton Index (it’s easier and cheaper, right?), which calls for a higher pH, but I read on these forums that you can’t use an in-line chlorinator with the high pH method. Why not?