My neighbors dog attacked my white leghorn hen a couple weeks back. She had several puncture wounds, and looked in awful condition.
First thing I did was separate her from the rest of the flock, because she was weak and I didn't want others to pick on her. Then I set up a cage in my house where I fed her water from a syringe (obviously no needle in it) and I began treating her wounds with hydrogen peroxide and this really good spray that is made for horses feet wounds but worked wonders on my hen. A couple weeks later, she was stronger and could eat and drink on her own. I did not expect this chicken to survive but she did. And to this day she is as good as new!
My advice to you, is to watch your chickens carefully. Maybe even have a talk with your neighbor about their dog. If you keep noticing any odd things examine the chicken from head to toe, just incase there are wounds you don't know about.
Also, try putting some vitamins or electrolytes in their water, just to assure they won't get any infections. I hope this helped! Just make sure to keep an eye on them and look for more symptoms.