Plants require 17 essential elements for growth:

Carbon (C)
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Magnesium (Mg)
Calcium (Ca)
Sulfur (S)
Boron (B)
Chlorine (Cl)
Copper (Cu)
Iron (Fe)
Manganese (Mn)
Molybdenum (Mo)
Nickel (Ni)
Zinc (Zn)

? Silicon (Si)

Let's break them down:

Hydrogen & Oxygen come from water

Carbon & Oxygen come from CO2 in the air

Nitrogen, Phosphorus & Potassium (N-P-K) are called macronutrients

We see numbers on all nutrient containers with 3 numbers such as 20-20-20

This means 20% N, 20% P, 20 % K

Then we have the secondary nutrients, Calcium (Ca), Magnesium(Mg), Sulfur (S)

Calcium can come from various sources- Calcium Nitrate Ca(NO3)2 , for eg, is very cheap

Epsom salts (MgSO4) are inexpensive, readily available & provide an ample source of both Magnesium & Sulfur

The micronutrients Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), & Zinc (Zn) are needed in relatively low amounts & there's usually enough when using a commercial fertilizer

You can also buy micronutrient supplements: https://www.amazon.com/Micronutrient-Nutrients-Simple-Lawn-Fertilizer/dp/B01N19BYG1

I believe in Canada fertilizers must display a "guaranteed minimum analysis" on the package

Usually on the back, this is the one for the micronutrient product listed above- all fertilizer products should have it, & you should pay attention to them

Also note "Derived from: "