Agreed that hay is for horses.
I'm with
@sunny747 too much nitrogen in later flower.
I've run many hydro systems and I never flush. I simply feed with the proper balance of nutrients as flowering progresses. One must cut back on nitrogen and increase phosphorous in late flower and the last few weeks any use of calmag should be suspended.
Witnesses will attest to the quality terpene levels, smooth smokability and high potency of my weed.
Perhaps flushing soil is required because it was overfed and underwatered the whole time causing build-ups, sans that situation, a flush is not required even in soil.