Swelling around the eye could be sinus infection or respiratory related... since you have others affected, I am inclined to think it's a contagious respiratory issue... if there is a foul smell, it could be Coryza, if not then I'd look up Mycoplasma... they'll need an antibiotic to get them better... *I think* Tylan or Oxytetracycline might help, but might want to read up on respiratory illnesses in chickens... Tylan and Oxy can be found in most feed stores, I believe...
I am guessing though... I hope this helps... or gets someone else's attention that might know more than me...
Sorry this is happening and hope they get better...