Several grows ago I brain-farted and went with high P and no N the last few weeks before harvest. All of a sudden my plants had no smell at all...it was like I was sniffing a rock. I re-introduced N and all of a sudden that beautiful sweet bud-smell returned.
This is currently my main "bloom" additive:
http://www.house-garden.us/products/additives/bud-xl/ which is 4-0-1, iow largely N.
"Will Bud XL help my plants if its used alone?
Bud XL will increase flower size. If used alone, Bud XL will only be able to utilize the nutrients within the medium. If used with a high PK late bloom additive, Bud XL will have optimal results."
Basically it fixes the messed up ratio after using PK13/14.
I now feed daily a NPK of 2-3-1 and I get no nute-burn or deficiencies all the way till the end
I'd rather go with something like 2-1-3 during late flowering, there's no point in a plant's cycle where it requires more P than N or K, not even close.
The irony is that N is important for the uptake of P and not supplying the medium with enough N can result in P deficiencies. Heck, it's the source of the P myth itself:
http://puyallup.wsu.edu/~linda chalker-scott/Horticultural Myths_files/Myths/Phosphate.pdf
The reason leaves look green to us are a direct result of the plant doing it's thing, creating buds that is. N is an essential element of chlorophyll = photosynthesis = photosynthate/sugars => buds. See my frost album for what happens when you keep feeding N and keep'm green till the end.
I know some growers who choose to stop feeding N early in flowering because they aim for a yellow harvest as it basically reduces the required amount of time to cure the chlorophyll (grass) out, which in turn allows them to sell it sooner (and not risk getting raided by the cops). The real problem there is not green leaves by drying and curing too fast. If you are going for the most potent quality and quantity, simply keep the plants healthy, as in green.