I'd add the additives last, presume it best to first let the parts A & B react. But others may actually know better, for real.
Regarding as your last step "add the base nutrients sensi bloom ph perfect in my case just to get good ph." No, you don't use base nutes to adjust pH. You shouldn't even be adjusting pH at all. pH Perfect involves the nutes being highly bioavailable over a wide range of pH. The whole point is that if you mix with low-salts water (and don't add too much salt supplements), the end pH of the mix simply doesn't matter. It's high salts, ppm, etc. that interfere with the pH Perfect part.
AN pH Perfect nutes do have some buffers and you should be seeing consistent pH after mixing. But again, the pH (within reason) doesn't matter.
Yes, many or even most AN users seem to manually adjust pH. But unless things have changed, the company recommends (if you ask a rep; otherwise they keep a very low profile on this point) not to adjust pH (presuming start with lower ppm/salts water), with adjustment just involving adding salts that interfere with pH Perfect working.