Fox Farm has many soil/coco products, but these are the most commonly used by marijuana growers:
Light Warrior - a nutrient-free soil intended just for seedlings
Happy Frog - a medium-nutrient soil
Ocean Forest - a nutrient-rich soil
When the plant is just a seedling, it can’t handle(and doesn’t need) a lot of nutrients, which is why the Light Warrior product exists. As it matures, it can handle more nutrients.
People most commonly just use Light Warrior and then transplant into Ocean Forest. You can do a two-layer soil combination so the roots grow into the Ocean Forest as it matures.
With the Ocean Forest soil, you shouldn’t need to give your plant any nutrients until it is well into the flowering stage.
Not that you have to do this, but I will just show you an example of how I layer all three soils: