Ask Mr. Smarty Plants

I'm glad to see that people utilize our Mr. Smarty Plants  questions database.

I found two previous questions, 4768 and 6477 that deal with Texas Sage and sooty mold. A recurring theme in both of them was that common names  can be tricky, and that aphid infestation can lead to sooty mold. Since the sooty mold question is less complicated, lets tackle it first.
Here are three sources of information about this problem. The University of California at Davis Integrated Pest Management Program has two good articles; one on sooty mold, and one on aphids. This article from the USDA tells how to recognize and control sooty mold.

Because your Texas Sage is growing in a pot with other plants, I tend to think that it might be Salvia texana (Texas sage) rather than Leucophyllum frutescens (Cenizo). According to its NPIN page Salvia texana blooms from March through May (so yours bloomed when it was supposed to), and is found naturally in dry limestone alkaline soils.There are 19 species of Sedum in our Native Plant Database, and most also prefer drier environments. The Platycodon, possibly P.grandiflorus  is a non-native that prefers well drained moist soil. You didn’t mention whether the Sedum or Platycodon had bloomed this year. Perhaps you are trying to grow three plants together whose growth requirements are incompatible.

You did mention that the Texas Sage was potted last year which brings up the possibility of transplant shock. (When were the other two plants potted?) These websites from gardeningknowhow.com and northscaping.com have information about transplant shock and how to deal with it. So your Texas Sage is dealing with the stress of being transplanted as well as having to compete with the other plants for space and resources. As general rule, stressed plants shouldn't be fertilized. Maybe it needs a pot of its own.

And don’t forget about the aphids.