You don't need to flush out all of the nutes in the miracle grow...(would be pretty tough given the slow-time release nutes). Some Nitrogen is good to have at the beginning of flowering (first 40%) because you're going to still experience vegetative growth (stretch)

I would slowly start to at the phosphorus (and not-as-much potash[potassium]), though.

What flowering nutes you plan on using?
:stoned: