Flushing for the last two weeks is debated, but on a sativa that has been fed for four months the salt buildup in the pot is real and a plain water finish does make the smoke smoother. Starting the flush too early on a strain that still has three weeks of ripening left just starves it. The finish timing table on https://hazesativaseeds.com pairs flush start dates with expected harvest weeks for the slower lines. Watch the fade, if the leaves yellow too fast you started too soon.