Body Checked Eggs

My young RSL, who just started laying a couple months ago, has started to produce body checked eggs. No signs of bronchitis or other illness. One of the causes of body checking (egg shell has a belt-like ridge, or set of ridges) is supposed to be stress towards the end of the day. Do any of you find that free ranging stresses your birds? Mine free range in the evening, because that's when we're home to be watchful. It could be that she's the bottom of the pecking order, too, but since I barter with my eggs, and give some away too, I'd sure like her to get back to smoother shells.

Any suggestions?