what's wrong with my hen

My hen, who's always been the top hen (a Barred Rock) has molted, feathered in wonderfully but has not started laying again. All others her age (second year of life) are back to normal. Roxy's comb is very small now, not nearly as red but other than that she is vigorous, free of parasites or bumble foot and does not have diarrhea. She has not lead the flock and stays on the periphery when treats are given, no more top hen. I have supplemented all of their diet with more protein during the molt and winter otherwise they forage and always have enough water and layer feed and oyster shell available.
Any thoughts about what I could do for her or what the problem is. It's like her hormones didn't turn back on when her feathers came back in.
Thanks