I just checked the local feed store and all they had was equine dewormer.
Any thoughts on which problem it likely was? I’d prefer to special order one thing that will work instead of several that may or may not be needed.
I'm glad she's doing better.For future, could I use the equine safe guard in a minuscule dose or is that too risky with the huge size difference?
I'd still give her the extra Calcium for several days to see if that helps.
Hard to know what's going on with her, there's so many things that can ail a hen. If she laid and is now doing better, I'd lean towards something reproductive. Could be the extra calcium helped but she may revert back over the next few days when the next egg is coming along.
Why a Miniscule dose of Safeguard Equine Paste? It's also 10% Fenbendazaole just like the Goat Dewormer. Instructions were given for paste or liquid dewormer.

For deworming, use an anthelmintic or get a fecal float to determine if deworming is necessary.
To treat most worms that poultry can have except for Tapeworm you can use Safeguard Liquid Goat Dewormer or Equine Paste (Fenbendazole) or Valbazen (Albendazole). Both are given orally by weight; they do not mix well with water.
Safeguard dose is 0.23ml per pound of weight given orally once a day for 5 days in a row.
---OR---
Valbazen dose is 0.08ml per pound of weight given orally once, then repeated in 10 days
Here's how to give oral medications:
https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/