Wouldn't worry about this mine does exactly the same thing year after year ,bought this about five years ago in a pot and it started to drop leaves after a week which i thought was a bit strange at the time , planted it out and low and behold every year since come the leaf break in spring it gets nicely established then for no reason i can see it tends to shed leaves alarmingly, all my other trees which surround it look fantastic as you would expect for the first spring flush then you look at the Ryuzu and you automatically think there is a problem? But as the months go by new growth always emerges to replace the "drops" and then it goes on through out the year and shows wonderfully in the fall. See pics of this years growth and new leaf after the initial "dropping" seem to think this is a trait of this cultivar, don't have any other cultivars which do this.
