If im not mistaken, purple lantana (lantana montevidensis) is supposed to look like that in (im guessing by central FL) zone 9. Here in 9b (central Cal) your description fits the look of this plant in the winter. Check out the pics of purple lantana at davesgarden. There is pic posted by someone in FL of almost black foliage of their lantana in winter (photo says it was posted on Jan 24, 2003)

Here is a link that might be useful: click here to view photos of lantana montevidensis

What you have described is normal for lantanas here in Central Florida, during Winter.
Felix