AsNoriuanswered grow question 3 years ago pH issue now doubts, if only with one plant - only bad watering could cause it. Then you got calcium lockout and leaves were burned under intense lightning.
I think you watered her while she was still wet.
It happened many times to me.
But : sometimes some plants are too sensitive to nutes and you were even increasing amounts ... Rare, but still possibility.
She is close to harvest, so just do flush for her and chop, hard trim jail awaits ;)
I have OCD for yellow leaves in buds ... ;))))
All the Best !