It does look like they're molting.  It normally starts at the neck.  Laying is usually affected by molt.  You treated with sevin dust, make sure you do the follow up too.  I would put a little at the bottom of the nest boxes too, then put nesting material on top.  Make sure you have free choice oyster shell available for them.  I would make sure they have shade too.  The skin can get sunburned during molt.  I had one that was so bad, I put a little sunscreen on her.  Get a bag of showbird feed, and mix it in with their regular feed, or spread it around generously as a treat for them.  I have found that supplementing their diet with showbird feed does wonders with feathering, and egg production during molt.  I wouldn't feed them the showbird feed exclusively though.  When the new feathers start coming in, try not to handle them much.  Did she have a rooster?