Your instrument has typical travel “relaxing” issues ?
Essentially all the tension was “lost” in the 2cm above the rim / below the notes and the bottom hole doesn’t resonate with the top note. Fairly typical over time. You may want to try an “push”up the metal below the notes that seem the worse. Usually with a rubber mallet, just tap gently but firmly with an upwards motion. Try not to tap the note itself but the lower 1-2 cm of it. This should not make dint’s, if so, soften the tapping. Every few 2-3 tap , monitor the sound of the note by tapping it whit a soft mallet or your fingers.
This trick might bring it back.
If your not comfortable trying this or it turns out to not work, then send it over and I will re-tune it 😉