Since Mericks is a live vaccine, I am not sure how well you can spread it to the adults from the chicks. I am not familar enough with the disease and the vaccination to say that you can or can't get chicks in the future that are not vaccinated. As far as I understand, once you get it, you always have to get chicks that are vaccinated, which is why they are not recommended for small flock owners. I also think that is is possible to get the disease from the vaccine since it is a live virus, and shipping stress just adds to their problem.
Getting chilled is often what spells end for chicks, but they can recover.
Make sure the shavings they are on, is a pure pine, not from treated woods, not cedar, and so on. Check feed for mold or if it is spoiled, and make sure they are eating, drinking, and staying warm enough. Beyond that, there is not much more you can do.
If the chick is really far down the line and does not look well, often letting them go is the best thing to do for them as it's my belief it's not fair to keep an animal around for your self, if it is obvoius the animal is suffering. However, if there is something that can be done, do it, as culling is a last resort.
As for cocci, there are types that do not have bloody poo, but do come with lethargic birds. If you suspect that, treating with sulmet or another coccodistant may be a last ditch thing to try.
