I noticed your losing color pretty good. I just re read your post in my diary. Because I used PH perfect line, my ph was always bang on. What’s your medium? Peat or coco? I see your running 6.6ph on runoff. Definitely too high for soilless. Phosphorous lockout is likely your culprit.
My issue was reverse, my ph on runoff gradually went down. You may want to look into what you can add to buffer the ph, and lower it. Phosphorous is quite important to flower growth.
Your pistils are still pretty young looking. How many weeks left you figure? Mine started going orange about 3-4 weeks before I chopped.
Looking like some nice buds forming! Your in for a treat come harvest time!