One of my girls became very lethargic after passing a shell-less egg like this. She continued to drink water, but was not eating well. I isolated her so the others would not pick on her. After many hours scanning the BYC forum, I decided that this was probably an internal laying problem and she had probably developed an infection. Based on information that others had posted, I used a nutritional supplement (Nutri-Drench Poultry) and a calcium drench (Goats Prefer). Because she was still drinking, I added vitamins and electrolytes to her water. She didn't want solid food, but would accept yogurt and fruit/oat baby food. I gave her amoxicillin for five days (I found the appropriate dosage based on her approximate weight.) After 6 days she looked much better and was beginning to eat solid food. She is now back to normal in terms of her behavior, but has not started laying again. After the trauma to her system, it's possible she will no longer lay -- this doesn't matter to me as she's a pretty bird and looks great roaming my yard!
I very much appreciate all the great advice posted here on the forum!