Coastal live oak illness?
 

I have a coastal live oak tree in my backyard, that until
recently has been in great health.
However, today I noticed some brown spots on
the leaves - in fact, this is quite widespread.
I posted a photo at:

http://www.dealfaro.com/~luca/oak_leaves.jpg

Nothing very special happened to the tree recently.
Below it there is some dry leaves-covered ground,
and (not adjacent to the trunk) a lawn that is
also somewhat dry.
Recently, the gardeners put a small amount of
fertilizer on that lawn, but that had been done
before without ill effect.

Any idea of what this is?
Thanks!

Luca

(You can also write me at luca ;at; dealfaro ;dot; com, which
works better than my yahoo address)