Nitrogen is the most abundant in terms of % for plant, Pottasium 2nd, Nitrogen is also the most sensitive in terms of toxicity of all the macro and micronutrients, once the plant stops veg growth and gets past the stretch the need for nitrogen is almost gone.
N & K share the largest nutrients highways or "channels", at a certain point in flower you want 100% of those channels pumping potassium up that channel, any nitrogen uptake detracts from the "capacity" of those channels, also any slow release nitrogen at this point as its no longer needed, coupled with nitrogen being very sensitive it can lead to toxicity.
Plants look beautiful and are you really feeding if tips are not a little burnt? :)
mid to late flower in a perfect world we want the soil void of nitrogen, this will also cause the plant to start cannibalising existing NITROGEN which is a "mobile nutrient" Once it is depleted from the soil the plant will "eat" or "reallocate" existing nitrogen within veg growth and use it to make new flowers, this is why you see some grows turn yellow ass the chlorophyll degrades other carotenoids, purples reds, yellows will show through, this will also help vastly with smoothness if performed in conjunction with a perfect long slow dry/cure.
hope it helps brothaaaaaaa from the big mother!