Looks like nitrogen has run low in your soil as it starts to fade from bottom upwards.
A water with a veg feed with nitrogen like Bio bizz grow might help it keep going and slow further fading.
Bio bizz soil ( and probably many other soils)is alot lighter( in nutrients especially nitrogen)than they used to be a decade back when we would stop Bio Grow food as soon as you flower, now best to give Bio grow up to 2 weeks into flower even more on nutrient heavy strains to keep them from yellowing 2-4 weeks early
A water with a veg feed with nitrogen like Bio bizz grow might help it keep going and slow further fading.
Bio bizz soil ( and probably many other soils)is alot lighter( in nutrients especially nitrogen)than they used to be a decade back when we would stop Bio Grow food as soon as you flower, now best to give Bio grow up to 2 weeks into flower even more on nutrient heavy strains to keep them from yellowing 2-4 weeks early