Nutrients during flower is a neccessity, otherwise your buds wont get the proper nutrients, thus youll get smaller, less potent budz. get ferts high in Potassium(K) and Phophorous(P), you will still need some Nitrogen to keep the plants green and healthy. I personally use Alaska Fish Emulsion for my Nitrogen source, and Alaska Mor Bloom for the (K)(P), but you can definitely use what you feel is neccessary. Get flower nutrients that say something like 0(N)-10(P)-10(K), you can go higher than that, but youd have to feed the plants smaller ratios. Combining some Veg nutes high in N with Flower nutrients is the best idea. good luck bro!