Answer:
Tsutaaja is grass, Pokabu is fire and Mijumaru is water.
Tsutaaja:
http://browse.deviantart.com/?q=Tsutaaja&order=9&offset=0#/d2pqbi9
Pokabu:
http://browse.deviantart.com/?q=pokabu&order=9&offset=24#/d2pj9z0
Mijumaru:
http://browse.deviantart.com/?qh=§ion=&q=Mijumaru#/d2prw5g