I've noticed that I have much greater success after beginning flowering. I believe that my fastest rooted clones were taken the day after my first(5-days in 12/12) bloom feeding(High P-K helps roots). My veg formula is 30-10-10, Whenever I take clones from a veg plant, I always have to baby them. I'm working on trying a 20-20-20 fert on a vegging plant to see if that helps with my cloning.