Patience seems to be making progress -- though still no egg in five days now.
Yesterday her primarily yellow-water poop turned more solid and normal appearing, and she began eating her poultry crumbles again. She seemed more alert and interested in her surroundings when ranging, with more giddy-up than she's had since this started.
The lack of egg production still has me worried, and I suppose she won't be "out of the woods" with this illness until I see eggs again. Am continuing her on the vitamins and de-wormer in her water.
Unfortunately, it appears I have an issue of bullying I have to sort out before I can put her back in with the others....
I will do some reading and start a new thread in the appropriate forum for that.