Lucas head in coco flowering stage help

I am on my first grow about to switch to flower. I have been using the Lucas head formula and the plants are loving it. My question is during flower do i change anything i am using gh micro and bloom with be adding koolbloom during flower. How much koolbloom to use per gal and when to start and stop adding it. Thanks a lot guys attaching pics of the girls to show progress.part0(23).jpg
 
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