Please help!

I have been looking on the forums to see if I can find something that matches the symptoms my 2 year old Australorp, Hildy, is experiencing.

She has had shell-less eggs in the past, but they were not that common. Last week, when I picked her up to greet her, a soft egg flew out of her vent. I thought she had simply pooped, but it was an egg and the other girls flocked to it, tore it apart, and ran around the chicken run eating it. I put Hildy down--she wanted to eat her egg, too, but the other girls wouldn't let her. I took this as her needing more calcium in her diet, so I hand-fed her oyster shells. I'll also crush up the egg shells and let her and the other girls eat them, too.

Every week, I do a deep clean of their coop and during these spring and summer months (I live in the Midwest), I'll mix in diatomaceous earth to help keep the mites at bay. However, I don't always sprinkle it in their nesting boxes, which is why I'm wondering if she has an infection in her vent.

These past few days, she just hasn't been herself. Her eyes are less bright, her comb a little pale. She will lay flat in the nesting box and not move. Usually if I go in to check on her while she's on the nest, she'll be more less upright and will always talk to me. The other morning, as one of her sisters came in to lay an egg, she was walking on Hildy's head and neck to squeeze in the box with her (my girls have multiple nesting boxes, but they only want to use the one that's already occupied). Hildy, the head hen, didn't protest this treatment. I thought she was dead.

When she isn't in the nesting box, she's out and about, foraging with the other girls. She'll eat and drink and put herself to bed when the sun starts to go down. She seems to be moving around without limping or slowing down. However, she isn't trilling/talking as much as she normally does. She'll sing the egg song for the other girls, but I'm not seeing any eggs from her.

I'm really concerned because Hildy is my pet--she's pretty much a feathered dog. We have such a strong bond, and I'm not ready to say goodbye. Is she egg bound? Is she sick? If she's sick, do I let the sickness pass or do I treat it aggressively? This has been going on cumulatively for about a week and a half (the soft egg that came out about a week or so ago, this sudden change since yesterday morning).

Not to overwhelm with too much detail, but we did also have sudden weather changes. This weekend, we were in the 90s and a few days ago, it dropped to the 60s with torrential rainstorms.

Any help is much appreciated. I can post photos up later if it helps. Thank you regardless.

 

Thank you both for responding. It looks like it was a calcium deficiency. Someone recommended giving her more calcium rich foods in addition to her oyster shells. She's older than my other girls (a survivor of a hawk attack, a dog attack, and three separate coyote attacks!), so I know her nutritional needs are a little bit different from the rest of the flock.
After giving her more calcium, her eggs are coming out more normal and are being laid. I'll continue to monitor her in case this happens again. Just to be on the safe side, I hauled out all of their shavings, scrubbed the coop down with some castile soap, and put in fresh shavings.
The other girls are still very protective of her--I'm not sure if it's because she's got something going on or if they're just protecting their alpha--my NHR struck me with her beak, causing a pretty decent gash and bruise on my leg.
Again, thank you for helping me. I'll update if things get worse.