It does look like bud rot where the main cola is turning brown. You can cut aorund it and remove everything from that little spot and it should help fix it from spreading so easily.
I would recommend a bud washing with a touch of peroxide in the water once your all done to help combat it from reappearing/spreading in cure.
Some of the leaves look like they have been burnt by the tips curling up and browning but they also look like they are fading from end of life. This all adds up as your plant is said to be 4 weeks past the last update, if the last update was on the 8th week we are looking at a plant in its 12th week of flower.
I would say its time for harvest.
Good Luck!
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