Similar with mine, was my 2 EEs and 1 mixed. They did not have any nasal discharge, or eye goop or any of the other symptoms of many of these respiratory illnesses. Just the coughing/sneezing and wheezing, lethargic - standing around with their tails down. Whatever it was the LA 200 sorted it out very quickly.It only affected my two EE out of 50 birds.
I’m not convinced it was MG or CRD.