Wait til about 40-50% of the pistils start turning brown, then quit feeding. It won't hurt anything if they go without nutes for 2 weeks or a little more, because there's still quite a bit left in the soil. Or, wait til about week 7, flush it and wait for it to finish. The longer it goes without nutes, the less it will have that 'grassy/hay' taste.
your telling me during the largest potential growth phase of the flowers you would cut nutes out?? for 2 weeks even?? wow... terrible advise....
first lets begin with the fact that the last couple weeks show the most significant swell... this means they NEED nutes... cutting them out, although wont hurt the plant, cuts the potential swelling the last couple weeks can bring...
second the grass/hay taste doesnt come at all from nutes.. it comes from a quick dry and a poor cure.. that taste is the chlorophyll in the plant that wasnt given proper time to turn to sugars.... quick drying and poor curing will result in that grassy flavor.. slow drying and curing right will always result in good tasting buds..
thirdly plants dont need flushed that long at all... really they dont.... if you "flush" the medium with 1/4 strength nutes the 2nd to last watering... and "flush" the medium again with plain water the final watering... thats all you need to do for a flush...
it makes me laugh to myself when i read about people cutting nutes out for so long from their plant... it really does limit the potential your plants have to grow those last few weeks.. hell i grow hydro, am planning on harvesting some girls this upcoming sunday, and still have them in full strength nutes.. i might let them run 48 hours with plain water... typically i would cut back to about 1/4 to 1/2 strength nutes the last 5 days and flush with plain water for 2.. but this is somewhat an experiment.. as i have done every grow.. to see how important flushing really is to the final product... and its becoming more and more apparent with every grow i do that i need to flush for less and less time.. i started out with 2 weeks plain water... lessened it to a week plain water... and just kept fucking with things until i got to how i do it now...
point being a lot of what you read is just another reader spitting out what they have been told to do... im giving advice based on experience..