It looks like pre-harvest fade (which is normal). If everything is in order like you said: Environment (temp, humidity), PH, feed schedule, etc. This strain is a 10-12 week strain according to the breeder, so you should see some yellowing of leaves during the last couple weeks of flower. Nothing you can do will stop the fade, don't increase the nutrients for sure. You could flush it and feed her a small amount if you feel necessary, but I don' t think it is yet. good luck and happy growing! 👊