Hen suddenly changes to laying a dark egg

[Ebarnes-21]

One of our hens just started laying a super dark egg a couple of weeks ago.

The colour is very unusual, like a barnevelder or maran egg for example?
Whereas the hens are a mix of sussex and hyline brown descendants.

I thought it must be a young hen, but after watching carefully it looks like an elder hen has suddenly changed her eggs to this unusual colour.
She's nearly 4 years old, she laid right through her first 2 years non-stop, hardly ever moults - she's amazing ... but she's always laid medium brown eggs, not chocolate brown ones!!

I wondered if a change in egg colour could indicate something about her health ... she seems fine but it's odd?

 

[ChickNanny13]

Could we get a picture of the difference in color?
Have read the color doesn't change although to bloom does, so maybe she being older the bloom is now thicker? Just guessing, waiting for others to reply. You wouldn't happen the have any of these in your flock ... Welsummers, Barnevelders, Penedesencas, and Marans

 

[aart]

but after watching carefully

Did you actually see the egg come out?

 

[McChooky]

I've read if things go wrong with the shell gland it can cause the eggs to become speckled but not so sure if the egg can change color.

 

[McChooky]

All my hens are brown egg layers but one lays a white egg occasionally and sometimes she lays a brown speckled egg.

 

[Ebarnes-21]

Didn't see the egg come out, no ... but now 3 or 4 times it happened in the same nest at the same time as that chicken, and the latest time the egg was still damp when she got out.
We've also eliminated 3 out of the 4 new hens from the suspect pool - those have been caught laying ordinary eggs.

Here's some pictures I took of one of the eggs ... my phone camera doesn't do the colour justice, but it also washes out the other brown eggs so the difference is still visible.

No I haven't had any of those brown egg laying breeds ...

 

[aart]

Didn't see the egg come out, no ... but now 3 or 4 times it happened in the same nest at the same time as that chicken, and the latest time the egg was still damp when she got out.

That sounds pretty sure.
Not sure why it happened tho.

 

[Crazyabouthens]

Hmm I have not idea what the problem is but I'm very intrigued to find out what the answer is so I'll be following along!

 

[The crazy Poultry hoarder]

Pretty eggs

 

[Perris]

We've also eliminated 3 out of the 4 new hens from the suspect pool - those have been caught laying ordinary eggs.

what breed is the 4th new hen? I'd wait till you are sure it's not her, before pursuing the hypothesis that an older hen has changed eggshell colour quite so dramatically as that photo suggests.