This happens because the algo is responding to vocabulary overlap with known trademarks in the system. "Delta airlines" and "Delta faucets" are a couple of "delta" trademarks that come immediately to mind. There may be more.
When I've had ads blocked this way, it's usually quick and easy for a human reviewer to recognize that my ad is about something different and doesn't infringe on any trademarks.
The situation can be frustrating, but don't stress about it. Just ask for your ad(s) to be reviewed then get on with something else that's productive.