As fruit grower says , you have a mainline running. good work. On the flip issue , keep feeding as a veg period until actual flowers form on the new growing tips. dont switch to bloom nutes until then or you will stunt their stretch period. If you prefer less stretch, not needed with a mainline as you want the shooting up growth from each top now , then you can use bloom nutes as soon as sex is shown by the two little white pistils that will show up around the joints in nodes , a few days into flipping if females . if you see any tiny elongated melon shapes starting to appear during this time then you have males. Ideally you are using female seeds and the likelihood of males is very low unless stressed out badly in some way. keep up the good work and have some confidence in your shown ability here. good luck