Definitely get the ta to 50ppm - that should be enough to keep ph stable but still not increase ph too greatly & bring any staining back.
You need to add sequestrant now to help take care of any leftover metals & prevent them from re depositing as you attempt to increase fc.
With your long drawn out exchange there’s bound to have been some mixing of old & new water.
Then you need some fc - the polyquat will only get you so far. Start low. Like 1ppm. Don’t jump back on with swcg just yet.
Stick with controlled manual doses.
You are about here in the process since you have completed a water exchange
From Aa treatment further reading:
“After AA Treatment
- Bring up your ph and alkalinity, - use Arm and Hammer Washing Soda first, it will raise both ph and alkalinity.
- Make sure you test in between, because you don't want your ph to go any higher than 7.2.
- If your alkalinity is in range, and you still need to raise your ph, use Borax to take it up to no higher than 7.2.
- You can start to bring up your chlorine. You want to do this slowly. It will take a lot of chlorine - preferably using liquid chlorine only at this time, and try to take it up to your minimum chlorine for your cya according to the Chlorine/CYA Chart.
- As you slowly raise the chlorine, watch for stains starting to form.
- If you see stains, make sure the ph is no higher than 7.2, and add more sequestering agent. You should see the stain lift in a couple of hours.
- Do not raise to SLAM FC levels! Do not do a SLAM for at least 2 weeks!
- Make sure you keep your ph low for (7.2) for a week or two - it won't be hard because the ascorbic acid and sequestering agent will help it stay low.
- Once your chlorine starts to hold, it means that you have used up the ascorbic acid in the water and it will be easy to rebalance the pool back to recommended levels.
Here are two important notes:
- High ph along with high chlorine will precipitate any metals that are not sequestered out of the water and on to the surface of the pool again. If this happens take the ph back down to 7, or 7.2 and add more sequestering agent. This should lift the stain off.
- You can add Polyquat 60 to the water before starting the stain treatment to avoid getting algae while the chlorine is low.”
Couple of questions-
How much cya have you added?
whats your filter looking like?