PK 13/14 now?

I start it at 0.3ml per litre at your stage( in Coco ) Then as the buds grow in size I will increase this once a week until I max it out at 1.5ml per litre in mid flower. Usually around week 5 or 6 in flower. Then will reduce feed once buds have fattened . I've never felt the need to go over 1.5ml per litre as it's strong stuff. Rember to lower your a and b as you increase your pk. As they don't require as much nitrogen after the stretch. I see you are feeding 3ml of a and b . That seems a little high to me. Lower than feed and add some pk 0.3/0.5ml per litre at your stage.