GMSgrowsanswered grow question 4 years ago I would wait until you have some nice nuggies before adding th ok. Best to stay with grow nutes until you see button size buds forming then switch over to flower nutes and a week or 2 after that add the pk13. Dont add it on top of your other nute increasing your ec, knock back your flower nutes some to keep your ec about the same. Cheers