Any Symbologist ... or Heraldic mage, or whatever you want to call them, learns about all of the elements, and constantly practices how to draw the crests. That much doesn't change for any beginner. But, as they develop and begin actually putting symbols together to form "spells," their individual affinity also takes hold. So, even if they put the same amount of practice into all of the elements, they'll discover that they have a natural strength towards certain elements.

...Or they find out that they're terrible at it. That happens, too. [wryly] But at least they get the tattoos for trying.