Terramycin is useless. You need to know what they have in order to treat it properly. My own personal policy, due to the serious carrier nature of most chicken diseases, is to cull and never treat. If it's viral, no antibiotic will do anything for it.
I just talked to an ag vet and he said to start everyone on Lincocin-Spectinomycin water solution. He said that it is an over the counter. Also said that my vet here should be able to do a eye swab and send off to check them. If I have one died then the ag vet wants to see the bird to check for things.
I hope that will not happen. He said that it is VERY common for backyard bird to come in as carriers even if you quaritine.