they turned 1 in March. Only the two buffs have missing feathers. All my SS are great. We got rid of several roosters yesterday so hopefully that will help speed their recovery. One buff is still broody but she gets out everyday for a quick bite and dust bathHow old are they and do you have a rooster? When my buffs were in their first year it was like their feathers were weak. I had to put saddles on them until their first molt. Their feathers are not likely going to grow back in two weeks and are less likely to start growing if they're broody. You can up their protein with high protein snacks or add in a higher protein food for a while. Make sure you keep oyster shell available as well.
Mites/lice can cause feather loss so you may want to just take a quick look. If you don't see any bugs then I would attribute this to having weaker feathers at the moment and wait for them to molt fully. Since mine had their first molt they have not had bare backs. (besides bare spots during the next molt)