I like the contrast/colors for fire, but I'd lighten up "wind" a little. Maybe change the color of the pants to a blue-ish-grey because that golden brown-like color looks a little out of place at the moment. The wind person looks too "solid", which is why I suggested making him lighter (or change the contrast.) And maybe add some other little details. Even just backgrounds or small tattoos to make them look different.
If you made backgrounds, I'd suggest *trying* to make wind seem nearly transparent on his background, and water translucent on his. */rambling*
Hmmm.. maybe ur both right.
It's better if I do something like this?
http://img167.imageshack.us/img167/7276/nobackground1me3.png
