For hydroguard, I like 3ml/gal. bottle says 2 i believe. Nice thing about h2o2 is that it will evaporate after a short time, so you can sterilize your system and then add the hydroguard after it's evaporated. For calmag, I only use 2ml/gal all the way through, and I do use ro water too. Sometimes I cut it out because I never see any deficiencies. In hydro you really need to measure your nutes by ec/ppm. Everyone's system is a little different, but there are commonalities. Using gh nutes, I max out at 1.4ec (700ppm .500 scale). They seem to be able to handle .8 to 1.0 early on without any problems. That's usually the ec when the roots hit the water. Around week 5 in flower they seem to like a lower ec, around 1.0 and a higher ph, closer to 6.0-6.2. Another tip I just remembered when the roots are still developing like that, I like to take a scoop of water a couple times a day from the bucket it's in and pour it over the top to give the roots not exposed to the water a dose of nutes. If you can get those roots to grow, the rest will take care of itself.