Now, I am very happy for you but all I can think of is, WHY DIDN"T YOU WAIT? Now, I say this because of the time frame of your posts and threads, you have not had them for long.
They need to never come in contact with him until it has been a few weeks. Not having indirect contact is good too. (Meaning you should wash your hands after doing anything with them, even just feeding them.) You yourself said they were sneezing and coughing. What if it is not just because of the move and they are sick? Every time you get a new rat (or most other pets for that matter. I even did it with my kittens) they need to be quarantined for at the very least a week, but best for two or three weeks. I am not trying to be mean, rain on your happiness, or scare you. But, quarantine is a must, if they have some, Novo could get it. Especially since he groomed them. He has possibly gotten their salvia in his mouth and picked up anything they have.
I will be nice to the pet stores and say, 8 out of 10 rats from a pet store will be sick. Most times with a RI. You need to keep a close eye on them. Sometimes it is hard to hear their breathing if the RI is just starting. Since you can not ask them to take a deep breath, you must make them take a deep breath so you can listen. Hold them in your hand around the middle section; making sure your hand is behind their front legs, around their chest and stomach. Squeeze gently. You will be contracting their lungs so they have to breath deeper and this will let you hear any small noises you would not have heard other wise. You're not hurting them, it is as if someone gave you a hug and squeezed a little too much and you had to put more effort into breathing. You do not have to do it for long. It actually works better if you squeeze a second or two, let go, and repeat a few more times. Just about every time with this technique I can diagnose a RI, even when it is just starting.
So, keep them away from him for two weeks, or more. Rushing into it is not worth it. It will cost you heartache, money, and worry time. Keep an eye on all three of them, watching and listening for signs or RI. I know you said Novo has already had a problem. In the rats I have taken in, the ones with RI’s are more susceptible to them, and the more likely a little cold or allergy when turn into an RI. You may need to take them to the vet or get some medicine for them. I would have them diagnosed by a vet if their symptoms get worse. Better safe then sorry.
I have had so many rats I have fostered that have been sick that the vet leveled with me. He told me that they give Tetracycline for RI’s, and instead of coming in every time (paying the office visit and the jacked up medicine price), to just go to the pet store and buy the one marked for birds (that is the only antibiotic they sell), make sure the dose is right, and follow the directions. But, he also knows I am a vet student and I have had so much experience with RI’s, that I can be sure not to give them medicine for every little sneeze. So, for years, I have been doing that with sick rats I take in and it works, I would have to say better, than the antibiotics the vets have given me.
I am sorry if I upset you or anything. I just do not want to see you or your ratties get hurt. I really am happy for you and I wish you the best.