I dont know... if they are deficient in N then giving them just enough to counter the deficiency might be ok. I will have to read up on how it works with N this far in flower.
I've got 2 tents, both in flower with one about 3 weeks ahead of the other and a few plants in each are showing yellow. I fill both tents water jugs at night and drop the air stone in it. Next morning i check PH and add a PH down to get it in the high 6 range, then that night add the Bio Canna slightly less then recommended dose. It generally brings down the PH in to the 6.3-6.5 range, then 15 minutes later i water.
Cheers, that's an excellent chart for sure. Though sometimes things dont exactly match, or match a few things so it still takes a bit of experience to come to the right conclusion.