Do you have nematodes?
Did you get that frost that we got here in LA about a month ago?
Renee

They aren't known for being particularly drought tolerant, and they prefer richer soils over sandy loams. See if keeping it better irrigated and well fed doesn't remedy the situation.

I used to have one and I also have sandy soil. Mine would wilt during hot weather. I say "used to have one" because I eventually cut it down because it was too much maintenance always having to prune it to keep it in check.

They also really appreciate plant food, so now would be a good time to give them some if you haven't for a while.

Here is a link that might be useful: San Diego Horticultural Society