strange egg shell markings!

In recent weeks we have been getting some strange eggs from one of our hens. It seems as if the shells are not forming correctly. Some look as though they were made by a pre-school child with paper mache!! They have lines and bumps and some of them have been a strange shape (sort big and long).

Please have a look at the photos and let me know if you have had anything similar and is there anything to be concerned about, like health issues for the guilty hen. The eggs are fine inside (yoke and white).

Any comments / advice welcome!

Joyful beat me to it as I was going to say that it looks like the egg an older hen may lay as they come in all shapes and sizes.

Thanks for your answer. You seem to be correct in you analysis.
The hens are Rhode Island red / white suusex hybrids from a local (free range) egg producer who last year was culling all their birds. I think they are 2 / 2-1/2 years old now. Since we have had them (last August) they have laid regularly every day with only the very occasional missed day. No break in laying through the winter months, so either we are treating them too well or they want to use up all their egg laying potential as soon as possible!

As an aside these hens do always seem to be 'on the go'. Never seem to relax and always wanting to get out of their run (which is a big space) and run around your legs hoping for some new food delight. It's not as though they don't have enough food. Just greedy guts!