Flushing in hydro is not necessary and could impact yields. I personally do plain water for the last day or two and thats it. Buds do most of their bulking in the last few weeks, and since the only nutes in hydro are the ones you put in, you would be effectively starving them during the time they need the most nutes. Keep feeding imo and wait until you see some amber trichs then do 1-3 days of plain water, though this step is not really necessary (I have smoked both "flushed" and non "flushed" plants and with a proper cure there was no difference in taste, or at least it was not enough for me to tell a difference).
"Flushing" before harvest has been a point of contention for a lot of folks so there may be some who disagree but after doing my own testing i came to the conclusion that it was not as necessary as i thought it was.
EDIT: Looking at your pic i dont see any buds. Is that a different plant or taken before flowering started?