Respiratory Issues but Lively Chickens?

[Cross B Hens N Heifers]

So I am about to bring home some very expensive young birds to create a breeding flock of BLRWs which will be kept in a seperate coop n pen but close to the others that are just for eggs. I’ve got probably 5-6 chickens that are still showing symptoms after a 5 day treatment of Baytrill given orally. I just got some Tylan 50 that I am going to give them next.
All of these chickens are healthy besides having a cough and a few having some clear drainage from the nostril. They are all eatting and drinking and very active. I am curious if this is a gram negative or gram positive issue or if this is a virus issue or just this hot humid weather?
They have also been getting electrolytes and probiotics in their water to help their gut.
I need to know what yalls opinion is because I am not going to let these new birds have a chance of getting sick from these birds.
Thank you for your time n comments.

 

[sourland]

I would be tempted to take one bird to a diagnostic facility so that the nature of the disease could be determined before adding valuable birds to your flock. @casportpony , can you help here ?

 

[casportpony]

Yeah, good advice. I would not bring home expensive birds until I knew what disease my sick ones had. I suggest you contact your state vet and find out how to get this done. You could also submit samples to this place:
http://www.zoologix.com/avian/Datasheets/PoultryRespiratoryPanel.htm

 

[Eggcessive]

I agree with getting some tested. Or you could sacrifice one that is sick to your state poultry lab for a necropsy to get a diagnosis. It could be a virus, such as infectious bronchitis, or a mild case of mycoplasma (MG) which is a bacterial like organism. IB can make them carriers for 5 months up to a year after all birds are well. IB can go through the flock over weeks or months. MG or CRD will make them carriers for life. Many backyard flocks are positive for MG, but no need to bring in new rare birds to expose them to it.