Two photos attached show problems. Not sure if both photos are attached so will forward second photo again.
Certified GKH Gardening Expert
These are Black Scale.
In the image these are the Adult female and they lay their eggs underneath them.
The eggs will hatch into 6 legged cream crawlers.
They like to host on Gardenia as well as Olives and Citrus Trees.
Here is a link with more information and how to treat.