your prespray is going to do a lot of suspending of soils and the nicotine and tar removal.
We have seen where along the edges if a colder climate and home, you will get soil filtration of the nicotine and it can be hard to remove like any other soil filtration.
You can sometimes scrub out those edges just on hands knees with a small brush, or rag...or carefully with a grout brush, but damage to the wall or baseboard is also a concern to deal with.
If there is a brown stain of some nature, it is going to be a tannin stain and something of an oxidizer like our Just Like Magic, Stain Magic, Stain Zone....gosh I am trying to think of other company products here, but there are others that can be applied to oxidize out the stain as well.