Lethargic chicken and mysterious white thing

[denisa1]

I got three hens and a rooster.The sick hen is 8 months old and she’s the smallest among the other hens.It worried me that maybe having eggs would cause problems for her since she was smaller than her breed usually is (bantam chickens).Weeks ago one day she suddenly became lethargic and ate only bit of corn so i feed her some canned tuna (she wouldn’t eat her poultry food) which she really enjoyed and gave her vitamin water and kept her inside a couple days at night.She got better after a few days.Today she stopped eating her poultry food and drank a lot of water which she “threw up” after i checked her crop too feel how much she ate.She made a clear runny poop and after that i gave two very small pieces of salami which she liked and later some boiled egg which she ate only a few pieces (she would normally get excited for it and eat a lot of it).She also moves slower than usually and keeps closing her eyes.When i last checked i found this near her:

I thought it was plastic at first.But i poked it with a stick and what i thought was water,was actually some goey liquid which makes me think that was supposed to be an egg.

Her crop was squishy even after she vomited the water but now (after i found this “thing”) i checked the crop again and it’s solid (not full but not soft and squishy like before).What is it and how can i help her?I really wish it’s not something lethal to her ....
She’s the black one and she’s one month younger than the other hen in the picture.

 

[denisa1]

I forgot to mention that she has never layed before while the other hens started laying this month.