I'm hydro. I won't be flushing BECAUSE the plants aren't taking any nutes right now. They're just drinking water. I haven't added nutes in almost two weeks. I just top off with water and the ppms have remained exactly the same. Since I know they're only drinking water, and less and less of this, too, they're sort of flushing themselves. Leaves are yellowing, but not in a nute-burn way. It's different. So I think they're just at the end of their life span, and this is their final stage. Sad for them, good for me.
Initially I had thought I'd drop the nutes down from 800ppm to 600ppm, then to 400, and maybe less since some people recommend that, but they're not taking them anyway, so I think it's a moot issue. I was on the fence about a true flush (changing the res to pure water) but I've read enough arguments that it's not necessary that I finally decided not to do it.
So right now I'm just riding this out as is...no more adding nutes, but I'm not going to take away what's there. Today marks the end of 7 weeks of flower, so I probably have another week or so.