You are in water! not soil so no worries . I have fed up to 5.7 in late veg  of micro  . That is on the high end. Heavy eater with a good light source. You will know when there is too much nutrients because your ph will drop  and will not stay steady. It is an easy bucket changeout fix if this accurse. Ph is the ticket. 

When I went to using GH Flora series I used the feed charts as a base , I would do the middle chart and go up and down from there till you find a feeding you like. Good Luck and Happy growing