She might be doing one of those slow molts where just the odd feathers get swapped out - Henny Penny does this rather than a whole bald body molt like Dorothy did.That is an interesting theory.
It seems more likely than anything else I have read. So far my reading suggested two possibilities. One was that their shells can get lighter and lighter in color and then reset when they molt. It feels a tad early in the year for that to be the case.
The second was various mineral deficiencies but that too seems very unlikely.
Edit: oh. Just read that it started before we lost Betty. I am stumped.
But Henny stops laying eggs when she does.