Hmmm..... bubbles. I didn't realize you were seeing bubbles.
I also didn't realize that they had it when you first got them. That's not good. If it was just a drive like you describe, I'm guessing that they had whatever it is before you ever got them, unfortunately.
I once got a couple of young cockerels shipped to me from what I thought was a good source. I had never had anything shipped before and thought I never would, but decided to try it. They looked very healthy, but one of them had a chronically "crusty" nostril area. It was obviously mucous that was getting caked over with feed or whatever. I would get a q-tip and wipe out the crust and it would just continue to return. There was thick mucous under the crust that I'd clear out and the next day it was back. (I also used some VetRX to no avail.
I ended up making a very hard decision to process both of them. It was hard because they looked and behaved very healthy. I think I had them here for about 5 weeks in quarantine before I did. But I had never had any discharge from any of my birds and this just wouldn't seem to go away. I didn't want to take a chance of getting something in the flock. Very frustrating.
I was going to send in a swab to the Purdue lab but ended up not doing it for a host of reasons.
If I were you in that situation and you have the time and energy, I think having them tested is the best option. That way you know and you can make a good decision.
eta:
I've heard way too many bad stories about folks getting started birds bringing illness with them. One of my friends had the same issue with started birds as well, and she didn't have the experience to be able to see there were problems when they picked them up.
I finally decided not to purchase any started birds again unless it was very special circumstances.
Again, frustratingg.