To treat them I would start them on an antibiotic that you can find at your feedstore--Tylan 50 , Gallimycin, Oxytetracycline, Spectinomycin, or Duramycin10. These will treat respiratory disease such as mycoplasma, coryza, and others. It's scary to think that this guy is probably spreading disease at every poultry show if he is a judge. Here is the disease link if you want to read it: http://edis.ifas.ufl.edu/ps044
X2.
And I would not worry about burning bridges. You will most likely not buy chicks from him again. I would be seriously thinking about if they carried other illnesses .
If you paid him with Paypal or Visa, you may have some recourse.