First off: 16 x 40 IG vinyl, about 6 weeks old.

I seem to have a problem with PH wanting to sit around 8 or above. My TA is 90. When we first installed the pool, I tested TA and everything else, TA was 80, and PB suggested increasing TA to around 130. He pointed to the information in the Pentair test kit that indicated if you use Cal Hypo, your TA should be 80 to 100ppm, and if you use Trichlor, your TA should be 120 - 140. At the time that was what I was using, so he added baking soda to shoot for around 120 - 130 TA. He said to get TA where I wanted it, and then see what happened with PH and adjust that if needed.

So, after adding the baking soda, TA went up to 130. In the last month since then, TA has been steadily dropping, and my PH wants to climb to somewhere between 8.0 and 8.4. I add muriatic acid, PH goes down to around 7.2, and within a couple of days, it's back up to around 8.0.

A couple of weeks ago, I took out the trichor sticks and switched to using bleach for regular sanitizing, and still using Cal-Hypo to shock. I've shocked a couple of times, trying to get rid of a little mustard algae, and to bring FL levels up during the huge amounts of rain we've had in the last couple of weeks. The information in the test kit says if I am using liquid chlorine, my TA should be around 80 - 100.

Should I try increasing my TA back up to 120 or so to prevent my PH from bouncing so much? If it stops bouncing, but wants to remain at 8.0 or above, should I keep adding muriatic acid? And then should I expect the PH to come down, but then remain more stable due to the higher TA? Am I overthinking this whole thing? I have been checking FC, TC, and PH levels every day. I am adding muriatic acid at least once every 2-3 days.

By the way, today's numbers:

FC 12 (added extra because we got 6 inches of rain from T.S. Alberto)
TC 12
PH 8.0
TA 90
CYA 40