The Cottage Smallholder

I have 2 hens, for over a year. We get 1 egg a day, have never had 2. I think the one hen that isnt laying may be egg-bound. She stands quietly with her tail down. She eats and drinks, and pecks at the leaves and weeds i throw in, has a nice red comb, then goes and stands quietly again. I cant see any swelling at the back end all looks fluffy and normal. Im new to hens and sorry if i sound niave but does the egg come from above or below where they poo from or is it even the same place? It looks ok. I cant actually handle them very easily due to the shape of their pen, as i cant physiaclly get in with them, but get very close up to see them through the mesh, if i was to reach in she soon moves! She can be like this in the morning, then by afternoon be tail up and happy again, until next morning when shes 'sad' again!