Could be several things....but generally swollen eyes, sinuses and faces in some sort of respiratory ailment. If it is ONLY the eyes, they could have simply eye infections, although many times eye infections can come from weakened immune systems to begin with, stemming from some bacterial infection. Respiratory in general.
If you could post a pic, it might be easier to diagnose. If these were my birds, and I felt they had a respiratory ailment, (other signs...runny noses, watery eyes, sneezing, coughing, wheezing, pale combs and faces, ect..) along with these swollen eyes, I would add antibacterial meds to their water for 7 to 10 days. Any of the (Mycin group of meds works well with respiratory issues) If the swelling appears to only be eye infections, (and usually the eyes will be cloudy with a simple eye infection) then I would apply some Terramycin Eye Ointment for a week until it cleared up.