Mystery...No other symptoms but a swollen eye!

[clandestinechix]

Has anyone experienced this? This is the 2nd one of my 5 girls that have had this in the past 3 weeks. Could they be pecking each other or throwing debris in their eyes? No other symptoms, no sneezing, no nasal discharge and no smell. They eat, lay and drink just fine. After reading about Coryza and MG I'm scared to death. The first girl was swollen about 3 days and then fine. The 2nd girl is going on day 3 and it's still swollen. Should I be worried? I was thinking about adding to my flock, but don't want to if I have Coryza or MG carriers.... Any advice is appreciated.

BTW my girls are Australorps about 10 months old.