Those are some seriously healthy looking plants, I do not believe a flush is necessary... that fine an edge of nute-burn means that they are consuming at least 99% percent of it. I would just back off a litle bit and see how things work... They look super healthy to me! In theory don't you want to feed them all the nutes they can handle, to maximize their potential? It isn't like they have brown burnt leaves, alittle yellow around the edge is not that bad in my opinion.

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