Id say give the topic a search on this forum, ive seen many posts discussing flower nutes and techniques, whether organics or synthetics. They definitely need some feeding tho by the looks of them. Usually in flower you want to feed higher doses of phosphorus and potassium and reign the nitrogen in. I use fox farms synthetics but they are known to cause issues with salt buildup and can derail a grow if not careful. If youre looking for a more organic feed, im sure others can help but it would probably be easier to search it and sift through old posts.