How much should an Australorp hen weigh?

[Donnigan]

One of my Australorp hens is looking a little thin so i weighed her and she is 4 pounds. She is the biggest eater in the flock! Is 4 pounds normal? She is about 2 years old and she doesn't have worms.

 

[Chicken Girl1]

I'm pretty sure the average is between 2.2 kg - 3.1 kg (which is like 4.9 lb - 6.5 lb).