Mark's Mac Air is slowing down and he wants to know if there's an app like SpinRite that can run them. Leo says that sold state drives (SSDs) use TRIM, or wear leveling to keep your SSD in good shape. It doesn't need to be defragged directly. But it will trigger the controller to run the TRIM utility. Search for TRIM in macOS. But it should happen automatically. If your OS is older though, you may need a third party app to do it.
TRIMFORCE Enable is the command you can use in terminal. That could speed it up.