One of my birds is molting for the first time. She is 2-1/2 years old. She is currently going through a dramatic, lose everything kind of molt. Is it strange that it took her so long? My other birds molted at one to 1-1/2 years of age.
Yes, I think it's strange that your hen didn't molt last fall when she was 1.5 years old.
A lot of the time I don't notice that my chickens are molting unless I watch them pretty closely. Chickens can do a gradual molt from head to tail, losing just a few and regrowing new ones as they go. Most of mine molt that way and I would never notice if one of them missed their fall molt.
This fall I've got a two year old that is doing the dramatic molt with feathers coming in all over the place. She looks horrible and seems very aware of the fact that she's not looking her best. Poor thing. Last year I didn't even notice her molt.