My alto or tenor will do that when the G# key is leaking. Try putting some cigarette paper between the pad and tonehole so the seal is maintained. If it is the only leak it should bring the D,E,F back and focus the lower notes.
I think that the seal is ok on the lower notes because it takes less pressure but more air to hit them, but it takes more pressure to hit D,E F and the seal is broken on the G#.
I think that the seal is ok on the lower notes because it takes less pressure but more air to hit them, but it takes more pressure to hit D,E F and the seal is broken on the G#.