Yes. Why don't you make it with Black like me and put
Gargos, Vicious Watcher,
Polukranos, Unchained and
Grakmaw, Skyclave Ravager? It's your call, but usually such decks like Wurms and Hydras are mainly Green with an adjacent color like Black or Red. White in your case is a bit a surprise (for me) and can easily be switched out with Black or Red. Black most definitely for Polukranos and Grakmaw, but Gargos is imperative in my opinion for your deck.
Ulasht, the Hate Seed is not good enough to justify it or make it tri-color for that manner. There aren't many Red hydras except it to speak of.
Regards:
Chavo