Start using it 4 weeks into bloom as directed. I use HESI and it starts with 2.5ml to 10L of water...and every week it doubles and week 7 it is up to 15ml to 10L.......you may need it before just have to watch the leaves, if they start to yellow a little like the tips of the leaves you need to start using it but a point to start is 4 weeks in and let me tell ya...........the buds will start to fill out like crazzzzzzy. Any questions let me know. have fun growing i know i do :jointsmile: