The warms temps can cause some loose/runny poop, but I agree with you, it looks mucousy. The Corid is a good idea and won't hurt her.
If possible, get a fecal float to be sure that there's still not a worm problem, likely not with your giving Fenbendazole for 5 days, but it's something you can...
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Can you post photos of her poop?
What did you deworm with - name of product, dose and duration.
Where are you located in the world?
To me she looks like a production hen, but hard to know.
Undigested pellets - is her crop emptying overnight? Does she have a source of grit...