I noticed yesterday my 5 Lohmann browns have runny noses; I got them on the 15th this month. They are about 12 months old. My 26 other chickens have no symptoms - 5 of these are Australorps who came from the same seller. The seller had vaccinated all of them against newcastle disease.
It has not been windy any greater than a gentle breeze. The temperature has been 30--35 celsius(86--95 fahrenheit) the past couple of days.
They have been laying almost everyday. They have no feather loss. They have been eating regularly, drinking normally, and run around energetically. Faces/wattles look fine, no swelling or unusual colouring. They have access to multiple community water sources, including a large pond. They sometimes peck the little ones and the ancona hens. They love the ancona rooster and hang with him often. They eat grass, bugs, etc. while free ranging and have a supplement of AGM Mixed Grains. They go to bed themselves with a full crop, jumping up the ladder of their coop just fine. Basically they appear healthy and strong in every other way.
Images of their grain mix. (I did not take these photos)
Images of their run can be seen here: http://www.backyardchickens.com/a/free-range-run-and-water-tank-coop
Some of them have more of the mucus on their noses than others. They sneeze on occasion, especially when they go to the coop at night, but otherwise seem to have no trouble breathing. I cleaned the snot off their noses today; it was crusted with dirt, but underneath that the liquid parts were thin and clear. There was a very faint foul odour. I only saw one of them poo, and it was clear, watery and had bubbles in it but that could be due to how much they are drinking to cope with the hot weather.
What should I do?