I meant to answer this.
I think there are only 2 questions in your query: how old and which one?
Even the experts argue about the differences so I sure wouldn't know. The flowers of L. diffusa are yellowish and the flowers of L. williamsii are pinkish.
They are mature at about golfball size; it can take 10 to 30 years to first bloom.
Watering once a week seems too often to me but if you are keeping them alive and healthy with that much water, it must be right.
