Toof Decay - 3rd Grow

Plants seem to be doing mostly well. One of the plants is showing some signs of a deficiency. The upper leaves are yellowing and spotting, and it almost looks like a normal late-flower fade. The pistils haven't started getting dark yet though so I don't think it's healthy. I did a light Sledgehammer flush this morning in case it's experiencing a nute lockout. The runoff PPM was high last watering so that is very likely. The flush got the pH and PPM back in range. I found a fungus gnat flying around the tent when I was watering during the week. I killed it and bought some sticky traps just in case there were more. It's been a few days and I haven't seen any others so I think I'm in the clear. Otherwise things are going smooth. One plant has mostly brown pistils and clear trichs. I'm guessing it has about 2-3 weeks left. The other plants are probably closer to 3-4 weeks from harvest. Just riding things out and hoping everything is smooth the rest of the grow.