Shiro Utsuris have temporary 'baby sumi' like many other varieties. As said above, you really need to wait until after the second growing season. At that point, disappearing sumi may be cause for serious concern... maybe not?

In regard to sumi 'rising', Omosako-san has commented that sometimes the sumi does not rise on the head until six or seven growing seasons. If it was there as tosai, and shadows of it can be seen as sansai, Omosako-san says to be patient. ...Easy for him to say. Not so easy for the hobbyist to do.