If you have already treated everyone with Corid once you shouldn't have to retreat them with it UNLESS you brough new bird in.
Your state lab should be able to walk you through swabbing a few birds throats to mail in for testing for MS too.
Call them on Tuesday.
You don't really need a near by vet to do testing. Your state lab can help...if you are in the US. What state are you in?
Sounds like you may have brought Marek's disease in with the Ayam Cemani.