Hi Captain, I just finished harvesting my Northern in coco/perlite with the same nutes as you and it was a very nice grow. I started flushing at end of week 8 for 1 week with the initial flush of 6 gallons of pHed RO water, went from 1400ppm down to 190 and then 2 gallons of pHed RO water every 2 days. Went from 190 down to 50ppm at the end. I should have went one more week because she was still a healthy green when I chopped. But Trichomes were milky with some ambers. Take your time my friend. Happy harvest 😎