I use Biobizz light mix and use no nutes except Biobizz root juice for the first 14 days. I use their fish mix instead of grow nutes and I only start adding that somewhere between day 14 and 21. I also add a little calmag from day 14 (about 0.5ml p/l to start with).
I start adding in bloom and top max when flowering starts. When that it’s depends on strain, but anytime between wk 3 and wk5. You will know when flowering is starting, first you’ll see pre-flowers- white pistoles start appearing at nodes, these sites gradually become like mini fluffy buds with lots of white pistoles - you’re in flower.