Hello ! So you must have a slight Calcium deficiency , as your upper leaves star to bleach up a bit. It is not the beggining of her fade , this phenomenon is called senescence and the plant discoloration would looks more homogeneous. I also noticed that you leaves have interveinal yellowing that makes me think about a Pagnesium def as well. If you just started to flush her then continue as those slight deficiencies will nor more affect you yield or the general health of your plant ! I hope it wiil help you ๐๐