Their powers are not truly "elements," nor are they Elemental Masters in the same sense the others are. Elemental essences. Note: The term "elemental essence" is conjecture based on creator statements. While it is a concept that exists in the Ninjago universe, it has not been given an official name.
Fire-elemental beings, for example, don't take too well to Water-elemental attacks. Similarly, Elemental Powers (especially the core four/five) are very competitive if not stronger than abstract elements because of the Inverse Law of Complexity to Power. Those with these powers may also have the ability of Elemental Absorption.
This is a list of all the characters of Ninjago: Masters of Spinjitzu.