Do you think I should treat them with Tylosin?
SMZ-TMP or bactrim can be useful for treating coryza and a few other diseases, but Tylosin, tetracycline drugs, and a couple of others are more likely to treat mycoplasma gallisepticum (MG, CRD.) If your chickens have a virus, such as infectious bronchitis or others, they won’t respond to SMZ. IB virus lasts about a month and usually grown hens recover.
Do you have to discard eggs?