You might try to elevate the feed and water. Put them up on a two inch riser. It will help everything cleaner.
Depending on how many chicks and whether they are bantam or large fowl, the chicks outgrow a brooder of this size in amazing speed. Even just 6 - 8, large fowl chicks will need an area 4 times that large in very short order. A small brooder area also makes it more difficult for the chicks to self regulate their warming needs.
A larger brooder allows the chicks to more toward the heat source if they are cool and get away from it if they are too hot. This is a vital element. It is very easy to over heat chicks. When it comes to brooder size, bigger, much bigger, is almost always better.