Sneezing freedom ranger chicks

[HuntingChick14]

I have 41 2.5 week old freedom ranger chicks. They've been sneezing pretty consistently for about a week now. I thought it was their bedding so I changed that, but the sneezing is persisting. I also observed today that a few of them had clear discharge coming from their nostrils. It was a very small amount and just looked like a little drop of water on their beak. I have them in a 2x5 section of my old coop on pine shavings. It was pretty dusty in there from my old chickens, but I cleaned it the best I could before putting them in there. There isn't any visible dust floating through the air or anything. Are they truly sick, or is this just a dust problem?

 

[BDutch]

Hard to tell, but I guess they have some kind of cold.

I had chicks once that all got a cold. Eventually they all healed. Some took about two weeks to heal, one up to 6 weeks.
I didn’t give any medicines. But gave some fresh greens on the side for extra vitamins.

I don’t have enough experiences to give a real advice. Some people said at that time to go to a vet. Others said don’t give antibiotics if you want strong chickens. I choose the last option. Two of these chickens are 8 years old now and never were sick since. (3 were cockerels and 1 hen was sold a few years later).
One of the pro vet people said I was lucky, if it had been a bacterial cold/ disease they all could have died.