I grow in N.E. also...what I do is wait till I see the white hairs (pistols)..,.when I see them I do my last Hi Nitrogen feed...then a week later I start my hi PK feeding with a low N value ..I use teas alot during flowering...Guano teas...with kelp and fish and alfalfa...and bone meal...
I can soil drench and foliar feed with tea and get great results....
Al