Those are quills that they are shedding and birds shed them all the time. They are probably the most common sheddings. Its totally normal, its just like us shedding hair.
The larger feathers (primaries, flight and tail) are shed more sporadically throughout the year depending on their molts. These are also often the most troublesome as they grow in as 'blood feathers', then as pin feathers and finally the actual feather itself. These are the ones that you really need to keep an eye out for, as far as damages go- but with plucking, the quills are more common.
Its still a good idea to keep an eye out for any unusual markings/bald spots or bloody feathers. I examine Skittles daily. He is always wanting 'pinnies' preened on his head.
In the meantime, here are a few suggestions as far as plucking goes.
If your bird is being plucked by the other bird, separate them. Birds preen each other all the time, but they shouldn't be plucking each other (you'll know if that is happening because the one being plucked will express their displeasure.) But based on the pictures you posted- its more them preening each other. I don't see anything that resembles plucking behavior- but take that with a grain of salt as I'm no expert on plucking.
Hope it helps you!
