Missing feathers, stopped laying

[3qkate]

My 1 year old Welsummer is missing some feathers on her back. This is new, and she's the only one in the flock of 13 missing any feathers. We do have a bantam rooster in with the hens. I can't say that she seems sick, but she definitely seems stressed. She hasn't laid an egg in at least 5 days, she seems a little more sedentary (not totally lethargic) still eating and drinking. It has been hot and humid here. I want to help her and don't know how. Any words of wisdom?

 

[aart]

It has been hot and humid here. I want to help her and don't know how.

Electrolyte/Vitamins....big ice blocks.
https://www.backyardchickens.com/articles/aarts-extreme-weather-spiel.75893/

Feather loss looks like rooster wear and/or pecking.
Some birds have more brittle feathers and are more susceptible to this.