Stop watering..
Trees this old don't really need much water they have deep root system that's in nice moist soil already..
It could be the water you are throwing at it or a bug problem.
If you are not sure on what to do the best and simple thing to do is leave her alone..

hmmm . . . . do you think there is any chance that the buds will return this season?

Hi Dustin - a 20 year old tree is a tough tree. Listen to Lopaka. Good luck and do post a picture of your tree.

And welcome to Southern California, where most every thing grows well!!

Kasie

She will flower again..
If you get no rain on her or no water from any other source for at least a week..
Mix some Peters "Super Blossom Booster 10-50-10 into a 5 gallon bucket and slowly pour it near her base of the trunk.
Make sure it doesn't run off and get wasted, if you have to poke a few holes near the trunk so that the Peters SBB drains into her then go ahead..
Relax and enjoy her blooms and don't worry plumies are almost bulletproof.
I find most trees when left alone bloom very well they just need full sun lots of it along with heat..
I have 7 trees myself so trust me :)
There are many other members in here that can give you great advice so good luck and enjoy!