Fear not, this is a natural process in which the trees replace old leaves with a new set. Since Live oaks are evergreen this can be alarming to some tree owners having the misconception that they don't shed their leaves all at once.
If you still have concern, just wait a few weeks and by then most of the new leaves will be out on the tree and it will look "new and improved." If it still looks sick let us know and we'll come out and take a look.