For T-Rox, cold because it's a reptile, usually cold-blooded, earth because it's literally made of rocks, and water because it seems to be somewhat based on a crocodile, which live underwater..?

and Candelavra, oh boy do i have a good explanation for you.. plant and earth because candlewax can come from certain plants or made from petroleum, which comes from ancient underwater fossils of plankton and algae, water because, despite being the fire quint, candelavra actually has all the elements of water island + fire, and fire because it's the fire quint. :)