with only seven spoiled little beasties we have a high certainty of seeing and noting any molts that would have occurred so this is not a case of mini molts going unnoticed. In this case her flight feathers are very ratty and broken having had them for well over a year. Additionally she never produced the winter down all the other girls did last fall, they all got distinctly fluffier and showed a beautiful cream color that she never had.
Anyhow, I can’t find any similar scenarios on the web except for the OP here, hoping they chime in on what happened way back in 2017!