My baby is 4 months and her tongue is always white. What can I do to clean it?

Looks like milk stain. Can use a clean soft handkerchief and wet it with water and gently clean it. Can also use the baby silicone baby finger toothbrush. You can also use the oral wipe if u like. Most importantly, if can after feed wipe the mouth for hygiene purpose. Once in the morning and night will do.