Tenant not keeping up with cleaning

[Renee Pratt]

While I was doing routine maintenance on an apartment that I rent out, I noticed my tenant is not cleaning the apartment at all. There is grime all over the kitchen floor. The grout that was once off white is now a dark brown. The stove top has dark burnt rings all over each of the burners. The bathroom is just as bad. Do I say something now, reminding them they are required to keep the apartment clean? Or do I handle this at the end of their lease with the hope they will clean it upon vacating the property? Currently they are month to month but they have lived there a year already. My lease states that they are required to "keep the property clean and safe." I don't have any other specifications as to how they are supposed to leave it in the end or how often they are to clean. Any help regarding this topic would be greatly appreciated!!