Brownish red gunk = iron -- a good thing to remove.

TA increased from 310 to 330 . . . but that might be testing error.
CH decreased from 370 to 340 . . . . which ALSO might be testing error.

However, since both values moved in the expected direction, probably not. I'd try again, with 2x the dose, and see what happens. Then, if it's successful again, you can decide if you want to do it 'for real'. What you don't want is to push the pH so high -- it's probably 9.0 now -- that you can't swim UNLESS it's a one-time event. So we don't want to test more than that before either going ahead, or waiting.

You probably want to read the muriatic acid sticky linked in my signature -- no matter how you go, you're going to end up needing some.