yep, you need all three. If you don't want to mess around, get Flora Nova. That's what i use and you only need two products, one for veg and one for flowering. Plus, it's waaaay more concentrated and its a mixture of organic and chemical ferts (better flavor). If you want to take a look at feeding schedules of both products go to this link: http://www.generalhydroponics.com/genhydro_US/feeding_charts/GH_KeepItSimple_DrainToWaste.pdfyou need all 3.
That's where i buy my stuff, but i go to the actual store. It's great. Call them and ask for CJ. He'll help you with any questions you got.High Tech Garden Supply has the nutrient starter kit by techna flora.