You grew for 6 weeks at 20/4, then went to a week at 18/6 and now a week at 24/0..........and you are wondering why your plant is acting weird??
18/6 from day one to harvest is optimal.
By slowing the plant down to 18/6, then accelerating it into over-drive at 24/0, you have forced it into cannabilizing itself, hence the yellow leaves........it is stripping itself of all available NPK due to being in overdrive.
Nothing you can do now to "fix" anyhting, the damage is done and the plant will not magically get better, no matter what you do......there simply isn't enough time before harvest maturity.
Be kind to your plant, go back to 18/6 and let her finish with the least amount of stress.
Whatever you do, do not cut any leaves off and do not try to "cure" her with strange concoctions of fertilizers.
Just continue on at a steady pace as to what you were feeding before, give her 18/6 and let her ride it out.