How do you tell if your chickens under weight?

[happyhens44]

When I get home from school, I feed and water my chickens. And Im reconizing that 2 of my hens ( there at the bottom of the pecking order) dont eat much, and I wanted to know is there any any simple ways to tell if there under weight? beside weighing them...

 

[coloradochick]

They say if you can feel the breast bone and it's prominent then they're under weight. Maybe try to feed them seperately for awhile