congratulations on your quakes!
To me this looks the start of over preening . Which quakers are very prone to. And could have started as reaction to being clipped, or if was in a pet store. As often quakers experience more stress in pet stores.
The good news , in your happy home environment, with lots to do, chew, and out of cage time, will likely stop. Because this is not been going on long. Offers baths in big shallow bowl or serving dish. Splashing around with hand often has them jump right in. Baths help some birds learn to preen in more normal manner. Never discourage preening as they do lots as normal.
A closer picture of feathers edges should show better if she has kinda chomped on them.
You won't see those perfect feathers till they molt out these.
My pet store baby was over preening, and had even started plucking her shoulders when I got her. Her feathers edges were a little black and chomped. This all turned right around as soon as she was home with me. And her feathers have stayed perfect for our 2 years so far. But she is still prone to a little nervous over preening with any household upset. And I think with her personality she could easily turn back to plucking if things ever went south for her.
Provide lots of easy to pick apart or destroy toys. Willow balls stuffed with shredded crinkled paper, Chinese finger traps, yucca chips, bird bagel, those rolls of csge weavers you can weave in cage bars or cut to 8 inch strips and tie to cage bars or a perch, chewable perches, or those perches they sell that are stuffed with shredded stuff.
Be careful with rope and rope toys. At least for mine she can't have any in her cage as she she picks them apart and really chews them up , unsafe as those threads can build up in crop cause a crop impaction. She is fine with rope perches while out of the cage. And nin of my other quakers bother their rope perches in cage. So you can try and observe, if she does remove them. And just attach on outside of cage.
Provide a upper corner roost, with something to provide a visual retreat. I provide the "safer, not perfect" non fuzzy sleep tents for all of mine. As quakers live year round in community nest in the wild. It has not induced hormones in mine, or eggs. I have 3 girls , and had one male. My pet store girl did lay an egg at 6 month old shortly after getting her from a perch. And this spring one in her food bowl. While my other 2 girls never have in 5 years or so that I've had them.
You do not have to provide a tent at all. I do, and I think helps reduce stress.
My re home quaker came to me never having one. But I was informed she had terrible night frights. And after her first night home she had a terrible one. So the next day I gave her a tent and never again has she had one in 5 years.
My rescue was 10-20 years old when I got her and had always had one a day still does.