Just an idea because it is hard to tell with the pink/purple lighting, but I had a magnesium and calcium deficiency when I was watering with reverse osmosis water and didn’t know to add calcium and magnesium to that type of water. The deficiencies were pretty bad and I did get it under control eventually but a lot of parts (both flower and leaves) were yellow and ended up getting bud rot at those parts.
Unfortunately when the deficiency gets so bad the part of the plant changes to brown/rust/yellow color that part of the leaf or flower doesn’t recover.
I trimmed as much of it out as I could with a small pair of clippers and then did a staggered harvest on the rest of the plant. Good Luck