Just to rehash your minor issue. The PH issue, because I went through this as a sophomore TFP follower. My PH level indicates on the test higher than it's actual number on any FC level above 5. So my preference is to keep CYA 40 or so, so that I can accurately test my PH immediately prior to my daily add of chlorine, since that's the time my FC is lowest and can get a good reading. Morevoer, if you look at SLAM steps, I'm pretty sure it instructs you to test and adjust PH before you start and then not test it again until you're done, because testing and/or adjusting PH while SLAMing is a terrible idea. So just wait until you've got things fixed before addressing the PH drift issue.
Notice I never mentioned TA when discussing PH. TA management, in my opinion, is not addressed correctly in TFP School or in any other pool management teaching that I've ever read. The problem with the way TA is taught is that everyone publishes a range, and as novice pool owners, when we see a range, we try to adhere to it. But that's not what we should do with TA. TA is simply a level that each pool owner adjusts at his/her specific best level to keep PH most stable within limits. If your pool has continual drifting PH upward, then the TA is too high. If your PH continually drops, then your TA is too low.
However, if you're currently fighting an algae problem and you've already started SLAM, then this is not the time to try and get your TA spot on, and when you do figure out which way that you move TA, then those adjustments need to be made very slowly and gradually so as not to over shoot that most-appropriate level. The way someone has already recommended to you to lower TA is the way I did it when I had the same problem; well, that is after chem geek finally explained to me that my TA did not have to fall in that recommended range. You add acid to get PH in range and continue to do that over and over. Eventually, the TA will find its way down to the point where PH quits drifting. When this happened to me, the PH quit drifting at TA 40. This is why I say that those published ranges are misleading and don't necessarily apply to everyone's pool all the time. But please don't measure and adjust PH until you show FC under 5 and then go slow and easy. If you take your time and get it set just right, PH necomes a non issue. I've not adjusted PH in a season and a half. Current TA is 60, but it wouldn't matter to me if it were 30. According to what Chem Geek told me back then, there is a lower limit that you don't want to go beyond; it's based on something called "carbonate alkalinity" or something to that effect, but for most people, they're not going to come close to that number. I think back then mine calculated in the upper 20s, and my PH stabilized at or about 40; so no big deal.
