@Pete12
I agree with the others. I don't think it would be a good idea to try to charge a cleaning fee retrospectively. You are likely to get the guests' backs up and risk a bad review and I doubt Airbnb will be on your side or help you in any way.
However, I would rate these guests down (a lot) on cleanliness, mention briefly in the review something along the lines of, "We were a bit shocked at the state they left the listing in. A lot more cleaning was required than normal," and explain to them in private feedback why.
At the same time though, I have to ask if you include any instructions/expectations in your house rules/house manual/check out instructions about what you expect guests to do in terms of cleaning up after themselves. If not, you need to have something there to make it clear. Although I would never dream of leaving an airbnb in that state, many guests think they've paid for maid service and don't need to lift a finger, i.e. it's just like a hotel, and probably don't even realise that leaving days' worth of dirty dishes is kind of not okay.