what type of nutrients to feed at the transition can be a subject with some different opinions. some say to just continue the grow nutes for a while, some say to switch straight to bloom, some say to balance them. i think it depends on the strain and rely on the plant to tell me. also, that 75 day countdown might as well be thrown out the window. i would focus on the buds and how they look along with the overall look of the plant to determine readiness. use the 75 days as a guideline rather than a final determining factor on when to harvest.