VetRx isn't a medication. But it is usually used as a supportive measure for colds and whatnot, and I highly recommend it as such. It will have absolutely no effect on eggs or meat. Not that you'd eat a sick bird.
But if you use it as a tonic or for healthy birds (it helps with dust related respiratory problems from beddings at shows, etc) the same - you can use immediately after using VetRx. You could yourself take VetRx. When I've had a cold, I consider it believe me!
As for terramycin, no - there is a withdrawal time as there should be with all antibiotics. Use their eggs to feed the chickens some treats so you don't waste the. Cook and freeze them for later use if you want for the birds.
By the way, I'm not a real big fan of terramycin. I really think the better meds are Tylan injectable and LS50. Antibiotics should always be used ONLY if you know for sure that the illness is respiratory, and then if the antibiotic is the right one for the bacteria (not virus, not fungi, not environmental cause) for which you're treating. Then only at the right dosage (not the "well i gave 2 teaspoons" dosage - but figured right off the package for treatment, not prevention) and then at the full strength, never "a bit or a sip of", and then for the full number of days - not one day short.
There's such a serious problem with antibiotic resistance. People all too often just jump on the antibiotics, especially terramycin, for anything. So take caution.
That's why I prefer to start using products like VetRx, probiotics, vitamin support, nutrition, environmental correction, etc first. Antibiotics should be your last resort when you absolutely HAVE to use them.
The only real precaution against disease is biosecurity, and not using antibiotics indesciminately, and hygiene.