It doesn't look awful, they could be side streets maybe? But you have a number of options here.
1) Narrow down the widest Street. You'll have to copy, delete and replace those buildings.
2) Widen the side streets. You'd realistically only have to the above process with the buildings on the corner.
3) Leave it as is. It's not awful looking to be honest.
4) Use the replace tool for every block to make it all sandstone
And a top tip for the future, build the roads first and the buildings after - that's what I find easiest.