Weird Egg- membrane on the outside?

[Crookadoodle]

I just found this egg in the coop, laid in the sand litter. I have 5 ameraucana hens that would be laying this colour and have been getting about 3 or 4 each day. One hen was previously sick in January and suffered a frostbite injury to her foot however has been doing alright now. I'm wondering if maybe she started laying again and thats why its a bit odd.
The egg looks like it has a second slimy membrane coating part of the way up the egg and then hanging off in a spiral. I washed it a bit and realized the membrane could peel off, and is a light green colour/tinted.
Is this concerning, is the egg safe to eat and should I be checking the girls for anything in particular?
(I will add the flock was just treated with pen-G mid March and a dewormed earlier in March to ged rid of round worms and staph, ecoli that was found in a necropsy back in February.)

Thanks!

 

[DobieLover]

I looks like this egg went back up the reproductive tract from the shell gland into the Isthmus and got a membrane put on it and then passed back through the shells gland to be laid. Weird. It should be fine to eat.

 

[Crookadoodle]

I looks like this egg went back up the reproductive tract from the shell gland into the Isthmus and got a membrane put on it and then passed back through the shells gland to be laid. Weird. It should be fine to eat.

Interesting! Thanks thats great info. Hopefully it was a one off for her.