Check out this chart:
https://www.google.ca/amp/s/www.loudclouds.co/plant-nutrient-deficiency-chart/%3famp
Potassium deficiency is my deduction. With a week or so to go, best to flush with distilled or pre-boiled tap water ph’d to 6. If you boil water, remember to let cool to room temperature.
For great results I use Green Planet Nutrients, absolutely love the stuff. Good job on your grow! 😁