U def had a ph problem before whether it is the water or the soil or both, and the worst thing to do before it is completely fixed/stabilized is to start feeding it nutes. It only compounds the problem. Things start to look like deficiencies not because they are not there, but because a high amount of something else being present is blocking the absorbtion from the plant. If your plant is still in the bucket, flush it! And, leaves do turn yellow during the advanced flowering stage, but naturally yellow, you wouldn't have any brown spots. Especially the way you do, lol. Ph often affects humidity next which is the perfect atmosphere for pests. I would def look into seeing if you have any pests flying or crawling around. Anything you plan on trying do one at a time, and give the plant time to correct itself before compounding the problem. I know I didn't exactly pinpoint your problem, but I hope this helps.