cal mag to final flush?

I am about to start my final flush on a couple of sweet tooths (or would that be teeth), a tangelo rapido and grape muerto. They have been under a Mars II 700 in a 3.5x3.5x6 tent. My question is, because they are under an LED, will I have to add cal mag to the flush or just straight ph'd water?

Straight Ph water

Flush* meaning nothing but water.... trying to wash away and have the plant eat the last of its nutes so I will start pulling from the leaves.. better taste. I have also grown all the way out and cropped with no flush. Had to cure for over a month but it was dank

Thanks,