Elongated eggs, sometimes with ridges and bumps

[Bruce61]

I have a Rhode Island Red that has very consistently laid elongated eggs, often with ridges and bumps. She just turned two years old, but all of her eggs since she started laying at around 18 weeks have been the same...very identifiable. Her eggshells have also consistently been thinner than the others' in the flock, and the yolk and whites don't seem to be as "tight". Same diet as everyone else in the coop. What's up with this? She's a very consistent layer, only takes one or two days off each week.