Cannabis needs 16 elements to grow. Carbon, hydrogen, and oxygen are supplied by air. The rest are not. I use Vitagrow a three part nutrient that is basically just repackaged calcium nitrate, monopotassium phosphate, and micronutrients. It provides everything a plant needs. It's a fraction of the price of most nutrient lines and grows beautiful plants. Nothing else is needed.
These are the plant nutrient requirements excluding carbon, hydrogen, and oxygen which is provided by air.
Macronutrients:
nitrogen
phoshphorus
potassium
Secondary nutrients:
calcium
magnesium
sulfur
Micronutrients:
boron
chlorine
copper
iron
manganese
molybdenum
zinc
As long as you provide these to your plants and give them a decent growing environment they will grow well. It really is that simple. You can buy into the hype and pay through the nose for a designer nutrient line and additives and deal with a dozen or so bottles of the same things I just listed watered down and put in shiny bottles with fancy labels. And then you are not guaranteed to grow decent plants. The Marijuana Plant Problems section of this forum is filled with people using designer nutrient lines and having nothing but problems, deficiencies, sick plants, etc... What you won't see in that section are people using inexpensive nutrients that provide all the plant needs. These would include VitaGrow, MegaCrop, Jacks Classic, etc... You never see people using these inexpensive nutrients posting problems. In fact all you're likely to see from people using these nutrients are pictures of beautiful healthy plants.