Check for mites/lice. Keep your coop sprayed or dusted every once in awhile since there are also mites that can live in the coop and come out at night. If they are itchy they will possibly pull feathers.
Are they bored? If they are in a small run you can hang a head of cabbage or get them a Flock Block. But the Flock Block doesn't have much protein in it.
Treats are usually around 10% of the total feed according to many posts on BYC and for my own experience, I would toss four chickens about a handful of scratch per day. A lighter weight hen eats about 4 oz. of feed per day. But scratch isn't what you are looking for right now, I am aware, since it is lower in protein.
You can't really feed too many scrambled eggs to them IMO. Eggs are nature's food for baby chicks, as the egg yolk is what the chick ate. So feed as much as you like. They are high in methionine, which if they are deficient in it, can cause feather picking.
They do need some grains/greens too, and variety, for their happiness and health. You can feed unmedicated chick starter or Flock Raiser (20% protein) if you wish, with oyster shell on the side to provide calcium.
I would give them some Black Oil Sunflower seeds, which are high in methionine. The other thing that can cause feather picking is lack of salt. Most feeds only have about 0.5% salt in them as birds have more trouble eliminating salt than we do. So if you want to add salt, you can put out some free choice kelp meal or Fertrell redmond mineral conditioner, or something else, but I wouldn' t recommend free choice salt - I tried that once and was kind of horrified at how much they ate.
I would also give them some grass clippings at 1-2 inches in length if you have them, unless they are free range.
http://msucares.com/poultry/management/poultry_pecking.html
http://www.livestrong.com/article/249591-foods-high-in-choline-methionine/