Did Ayu's voice/singing style change?

[PrincessAyu]

I wonder if her voice or singing style changed. When I heard Born To Be... at the Arena Tour 06 I thought her voice sounded deeper/heavier and had a lot of vibrato sounding much heavier than her usual vibrato. At some points she gets really low with her tone and it sounds as if it suddenly is so difficult to sing what she's singing, while usually her voice is very light and controlled. It seemed a bit off in AT06. I wonder if anyone noticed this?

I compared Born To Be and Startin' lives to the Arena Tour and in the lives (frm March 2006) she seems to have a much lighter and controlled way of singing.

An example is in Startin' when she sings "totemo suki dakedo" before the "Dreamin', Startin'.." part begins. Her voice sounds really "weird" when she sings "dakedo" in AT06. Deep and strained or so. I can't really describe it. What do you think?

EDIT

In STEP you, she sings like she did before again. As in lighter voice and all. So was Ayu singing just outrageous/uncontrolled before? Cause I know that in "Startin'" she sounds like in Born To Be... again.