It’s also possible that the recorder is slipping a little bit without your realizing it. This might be leading to your right hand fingers changing shape and not covering the holes properly in your attempt to hold on to the instrument. You might need a thumb rest. To help you figure out whether or not you might benefit from using one, wrap a rubber band around the body of the instrument and position it where the upper edge of your right thumb normally goes. It will keep your thumb from slipping and, in turn, keep it from gripping too hard. This might enable your right hand to feel more comfortable so that your fingers can then cover the lower holes more accurately. I use rubber band thumb anti-slip rests on my heavier recorders. It may look a bit funny, but hey, who cares if it works?