Define pools. Horses get colds but that generally doesn't involve enough drainage to hit the ground. From what you are describing, it doesn't sound like a cold.
Panic over I think.....Emma said she had been drinking not long before I got there and the chased a chicken away from her feed, when I went back out after posting I had only got 1/2 way across the field when she sneezed LOUDLY! She is now eating, drainage has stopped and she seems happy! I will keep an eye on her, but I believe she may have had a nose full of feathers!
Mine have had an occasional cough... commonly at the first start of work, like a clearing of the airways... I saw gunk come out of Cyn at one of these coughs. I attributed it to dust in their bedding and hay as we got down to the end of the old hay. It's hard to tell sometimes, who coughed, but think I've heard it from both Bay and Cyn.
But a runny nose, if it had any color other than clear, I'd be concerned about.