Yesterday I noticed that my favorite rooster had a runny nose - clear and watery. Scared me to death after reading about all these illnesses amongst chickens lately.
So I came to this forum and did a search on "runny nose" - it pulled up several pages, but I read through each and every one and by the 2nd page I found the answer. Search for "runny nose" and then read all of the threads it pulls up.
In my case, SpeckledHen explained that sometimes allergens, pollution, and other things in the air can cause a clear, watery discharge. I recalled that we had the wood stove burning and my rooster was in the smoke when I looked out the window, shortly before I discovered his nose was running. It was clear and very watery. After reading what SpeckledHen posted, I went back outside and the runny nose had cleared up.
I don't know the answer to your question, but searching on "runny nose" may give you a better idea. You just have to read through every posts on every thread.
Best of luck,
Penny