@Mandy324 No, Airbnb doesn't add a cleaning fee or a linen fee. This is up to the host.
Anything you change in your listing, be it the cleaning fee or the cancellation policy, or whatever, only applies to bookings made after the changes were made. Reservations you already have can't be charged more than what the charges were when they booked.
Hosts often find that their settings have mysteriously changed on their own through some tech glitch. It's wise to check all your settings and charges frequently.