Lethargic Hen, not eating, lays soft eggs - Help!

Loretta has a history of laying shell-less and soft eggs. This morning, she did not come down from the roost with the other girls, but appeared to "sleep late." When she did come down, she was moving very slowly.  While everyone else ate, she just stood there.  Then she "pooped" something watery, waited a minute or two, and dropped a soft egg on the ground.  She walked around a little, but mostly stood around like a statute.  I tried to bribe her with mealworms, and she didn't even care about that.  She did drink a little water and then went back up into the coop and nesting box.  

Yesterday, I did give her some yogurt with calcium supplement.  Some of the other girls ate it too, and they are fine, so I don't think that had anything to do with this. 

Any thoughts? Suggestions?  She clearly is not herself today. 

I appreciate any ideas. She is a sweet girl, bottom of the pecking order, and just a year old. We would hate to lose her. 

Seems to be doing better now.  She is out with the other girls, acting like her normal self.  I'm still interested in thoughts about what could be going on with her, if anyone has ideas to share. 

Thanks

To me, this isn't about egg laying behavior - it became an emergency when she became lethargic - that's why I posted it here under "emergencies."  But thanks for your suggestion. And yes, I had already searched throughout the forum and found nothing that answered my question, which is why I posted it in the first place. I'm a little frustrated that not one person in this whole forum bothered to offer any help at all. Surely, there has to be one experienced chicken person out there who could have offered some advice! :(

Fortunately, it didn't matter.  Whatever was going on with Loretta, it passed, and she was fine. She continues to have issues with calcium deficiency, so I make sure she gets dairy treats to supplement.