Hello!
You said that your drive-up units are all rented. I would switch it around and raise the price on the drive-up ones just a tad to make the hallway ones seem more appealing.
Our other property has the same issue but they are two story! Hallways and 2nd level
We did some unit conversions for some bigger sizes because that is what was in demand. Also we did the local college campus flyer handout thing as well. Seems to be doing good now. And lowered the rates on the inside ones.