looks like a heat issue to me as some of the leaves at the top are pointing up, canoeing and have crispy tips. some strains like it cooler in bloom, some like it arid, not too humid, some prefer a constant breeze etc. The strain is typically the key. If your nutrient schedule has been the same all along it could be a build up.
At this point flushing is what you needed to do. I wouldn't keep adding nutes, just properly PH'd water and check your temps aren't too high and see what happens in a week or two.
If they are root bound as someone mentioned, there is little you can do unless you really want to transplant them to bigger pots