Some website builders lower the resolution of pictures when you upload them to the server. Now that you are copying and saving them from your website you are now saving them in the lower resolution. When you upload them to the Airbnb server they get changed again to Airbnb's standards. All of this compression can destroy a good picture. Best to retake your pictures and use fresh ones for Airbnb even if it is more work. In addition, check to see if Airbnb will send a photographer to your house free of charge. (https://www.airbnb.com/info/photography)
One more thing, Airbnb recommends photos that are at least 1024 x 683 pixels with a resolution of at least 300 pixels per inch. A wrong size picture will also result in a blurry phot on the Airbnb website.