I have five hens who live very happily in the 3 X 5 hen house on wheels (Chez Shelly) that my husband built for me. My question is about the size of the run we attached. Since it's built on a wagon base, we move it every day to the pasture, the garden and in the yard. The girls get fresh green stuff to scratch and bugs to eat every day--but the run is only 3' X 6'. They don't seem to mind, but now that they are 18 weeks old they practically fill it up when they are all outside. Should it be bigger?