Your area is chalk full of commercial potential, it's also chalk full of commercial competition. That being said.....it's time to hit the bricks and let them know you're there.
Personally I find more profit in the residential side of this equation. It takes less time, effort, labor, etc. and produces more profit than commercial work.......In my opinion of course.
It really comes down to a few things.....
How is your website ranking? How are you producing residential-commercial traffic & sales? How long have you been in business in the Charlotte area? Not that there's anything wrong with this....are you part-time or full-time washing?
This quote kind of sticks out to me "Our best leads come when people see our truck in a neighborhood." ....not that there's anything wrong with that situation...but normally that's not the way it happens....it says there's something wrong with "Lead Generation" in your business model....At least to me....with no disrespect intended.
Your thread says to me that you've got a Marketing problem on the residential side of this. It may stem from any one of the things I've listed, or something else...I'm not quite sure....but it's a good idea to take a step back and look at this.
As Always....Just Saying...