I'm afraid there's not much to be done - Vivian. Of lately, ppl with same problem as yours are on the increase. As you are, you are doing all OK from what I could see at 1st look; 'great host, super clean, good location and EVEN BETTER than the PHOTOS' your guests say...'
However try to 'protect rating as much as you can [someone did hurt yours, somehow] and not letting fall under 4.5 if possible. This might help to explain importance/ how it works;
https://community.withairbnb.com/t5/Community-Cafe/Unfair-Overall-Rating-Calculations/td-p/1503019Wh... is the moral of the story?
There's not 1single reason for 'fallen bookings' and many we mention here, no one is 100% sure. Some can be: competition [hosts in same area are on the increase] 2nd houses [many ppl bought during pandemic and now Aibrnb them] pro-hosts [with several listings] hotels are lowering prices and in some areas are cheaper; oil crisis, more cautious guests, 'specifics' PEOPLE WHO ARE ABLE to offer things 'above average/ experiences, pools etc' and so on; but how is GOING is not bad...so keep faith [unless a Full recessions hits and then AIRBNB will be in real trouble]
So, what do people in your position do? Some do tweaks, offer Instant Booking [cautious here, as some hosts wont advice/ use it lightly] lowers prices and cleaning fees [or remove them completely] offer some extras etc etc. G.Luck