yeah... i mean... even if you check em an shit its good to know when they really need the extra boost of nutes the worst..... i am thinking like early flowering? i mean most people start to back down on the nutes in the end i think
i'd say nutes are important throughout the entire process for the optimum plant, but if your strapped for cash and want to cut some corners i'd definitely say during flowering.
To make it short I would say,nutes throughout the whole grow.You would want to hit them good during veg.,that way you get more flowering locations.Then during flowering change to a good flowering nute.Something to sweeten,and bulk up your flowers.Anyway,thats my two cents.