Help, my miniature lilacs are dying!

I was away on vacation and came back to find one of my miniature lilac bushes totally dead - the other has brownish, copper colored spots on the backs of some of the leaves and looks like it is starting to die as well.

What do you recommend?

Without some pictures and knowing a bit more about where you are geographically, and how old these bushes are, and how well established it's almost impossible to give you any advice. You do know that these are deciduous, right? In the fall, or even in the late summer they can start to dry out and lose their leaves if it's been a very dry summer, or excessively hot.

Sorry I can't be of more help; post again with more details (and pictures if possible) and I'll see if something jumps out at me.

Best of luck with your Syringa!
Jacki