As told before when Kea tried to curse an innocent man long ago (though his innocents was unknown to Kea) it backfired and was sent back to Kea, though warped. And from then on he was colorblind.

Something similar happened to Whetu.
She to unknowingly tried to curse an innocent, but hers was a bit different...

Instead of going colorblind she is now no longer able to physically feel anything.