You've likely been given misinformation about flushing. I personally think there is no need to "flush" a plant kind of the same way a mechanic will not recommend you totally flush your transmission. It can cause issues. But I grow fully organic in soil. so will be different than someone who rows in coco coir. and if you are growing organically you do not want to wash away all those valuable nutrients. what's inside the plant is in there. there is no flushing that out. if you are feeding some sort of water soluble nutrients then i would stop and do water only. you could call that flushing but its not really flushing anything out. unless you do what some people do, and keep running water through your soil until it runs clear. i would never do that. its just a waste of water, and nutrients like a said. the plant should naturally start to take up less nutrients and start to use what's available in its body.
The stage of your plant she looks lie she's doing very well and no need to feed anymore she's maybe 2 weeks from harvest. if you taper off the feeding then you should start to get some fade on it depending on the genetic. I do however believe in using slightly colder water towards the end. to mimic nature and the cold rains going into winter, i thin that help trigger the senescence process, which is what you want.