Hen in need of help.

[Min-pin]

I have two hens who have feathers missing. They are 3 years old and never had any problems. I checked them both well for bugs and nothing. We gave them treats to see if anyone was picking on them. No problems. They all ate in peace. I keep our run and coops clean. We do not have a rooster just 12 hens. They are well taken care of and very friendly. They love to be petted and line up for them.
Are they being attacked all of a sudden or am I missing something. I’m going to put a camera out there to see if I can see what’s going on. Is there something I can put on them that will help it heal. And protect them from further problems? Any ideas would be amazing. I have had chickens my whole life and never experienced this before.