if I were you , I would start my flush in 10 days, and just use plain ph water . your plants look very health . you can flush 3 weeks with out any problems, point is start the flush in 10 days, and keep on flushing them my guess they will be done with in a week or so after you start to flush, and if you ever run into trouble last 2 weeks of flowering most common time for problems ! mold, herming. so any problems arise you can harvest any time, they have to be flushed regardless, my advice is from over 15 years experience,