Yes, that is what I have noticed too, fine and active, then a quick death. I was always told it was a heart defect, and they have a heart attack. I would never treat such a bird. While they are good, they are fine, and it is a quick end. I would try and not hatch her eggs.
I think that treatment might just prolong it. To each his own. Sometimes I think people on here have an unrealistic hope for very long lived birds. Most hatchery birds on average live about 3 years. Before you disagree with me, remember average will have many birds that don't live that long, and many birds that live longer.
So yes, I think something is wrong, no I don't think you can do anything about it, nor should try. Give the bird good food and water and enough space and that is enough.
Mrs K