Oddly textured, thin shelled eggs

[Paradisewife]

We have a flock of 7 hens that turned 3 yrs in April. The 3 poofy heads lay white (1 Polish & 2 Houdan), 2 Faverolles lay brown, 1 Cream Legbar lays blue, and the easter egger lays a light pinkish brown, and I know who lays which egg. (Sorry, bragging on my babies)

3 days ago, (7th) we found Stella (1 of the Houdans), trying to expel the (fortunately) unshelled membrane of a ruptured egg (this has happened to her a couple of times before). The liquid egg dribbled on her feathers was still wet so Jason did a quick internal check for shell but found none & did a quick cleanup. She wasn't very stressed so we gave her a few minutes & she expelled the membrane on her own (complete) and within 10-15 minutes, she was back to her normal self. And laid a 'normal' egg 2 days later and again today.

I could easily give a detailed historybut will *try* to spare you.

The heavily rippled egg from the 3rd is not at all rough or sandy feeling, just smooth ripples. A light tap with a fingernail sounds thin-shelled, a heavier tap will break it. The lightly textured egg from the 6th isn't gritty or grainy feeling either, and is more fragile.
The normal feeling eggs are thicker shelled.

There is a history of occasional nest breakage, but these girls eat every scrap of shell, so we never knew who's egg.

Speaking of shell, oyster shell is (always) available in abundance, they are fed layer feed, mixed seed scratch (we add other seeds to commercial scratch blends - a little millet, safflower, sunflower varying by season), and fresh fruits and/or vegetables daily. Mealworms & hemp seeds as treats.

So, is there a lack of, or excess of any particular nutrient(s) that I can correct? Or is it genetics?

Thanks!
(My Polish lays rather roundish eggs, and her hatchmate's were even rounder. We lost her at 17 months...chronic severe prolapse, and we involved our vet early on.)

 

[Perris]

There is an illness working through the flock. Ripples on the shell is a classic symptom.

Edited to add link to a page with various common types of abnormality
https://extension.uga.edu/publicati...egg-abnormalities-how-they-affect-egg-quality

 

[Altairsky]

Yes there might be an infection of some sort. If no serious symptoms appear, it will go away on its own. It might take up to 3 weeks.
One of my hens got a few sneezes, probably a respiratory virus with very mild symptoms but she laid sterile glitched eggs for a whole week.

 

[Paradisewife]

Yes there might be an infection of some sort. If no serious symptoms appear, it will go away on its own. It might take up to 3 weeks.
One of my hens got a few sneezes, probably a respiratory virus with very mild symptoms but she laid sterile glitched eggs for a whole week.

Thank you. She's always been healthy, and Jason (my partner in chicken madness, codependently supporting each other's chicken math) loves his Houdans, and spots everything. It has happened before, as recently as 2 weeks ago, and last spring when we thought squirrels were breaking/stealing eggs. She had a couple of 'remove-the-shell-remnants' episodes, about a month apart.
The squirrels actually were stealing the eggs and sometimes breaking them in the process. We found 2 that had aparently been rolled through the 2"×4" welded wire fencing...and just... left? Unbroken. A couple of the harder-shelled eggs. Then there are the fat- footed girls that want to lay with the group, who inadvertently smash thin shelled eggs with just a toe..

And thinking about it all, it seems that all of this varying calcium use on her shells coincided, last year and this, with our first few  really hot weeks.
Things that make you go hmmmm.
??