I would assume that also but just to be on the safe side check your birds at night after they roost for any pests. Some only come out at night and feed on the birds and hide in their coop during the day. I use a headlamp so I have both of my hands free to inspect the birds. I also take a paper towel and rub it on and under the roosts and look for streaks on the towel which could be a sign of mites. Good luck and have fun with your birds...
I also agree it looks to be that some of the damage is from over breeding. I would give the birds a higher protein feed as their feathers are primarily made of protein, Many game bird feeds are higher in protein and it won't hurt the birds. Again, good luck...