Sickness and no production

Hi all,

My first post here. I am new to this game, but I am enjoying it. I had a flock of 11 hens, different breeds. Egg production was going well, about 6-8 eggs per day. Then about 2 weeks ago I found a dead bird in the run. The next day I noticed that another bird was laying down with a clear discharge coming from the nostrils. She later died. I am guessing some sort of respiratory infection. Two other birds looked listless and laid down a lot with no noticeable discharge though. I did not give any antibiotics, only added apple cider vinegar to water. The sick chickens seem to have recovered, eating well and foraging. The problem is that to my best guess they and at least two others have stopped laying eggs. I am sure about one that has stopped laying, as she is an Ameraucana and I have two of them and never get more than one egg every 2 days or so. I never catch the birds in question in the nest box. Any idea why the egg production ceased.