Didn't mean to say a "bad word" and scare you! I know the feeling though. Everytime one of mine sneezes, I stare at them and wonder, lol! I had pox last year, and that was a nightmare, but I didn't lose a single bird. Even the chicks breezed through it. I've thought about vaccinating for things, but I'm just not sure. There are mixed opinions. In fact, I have the pox vaccine in my fridge, and was planning on giving it, but had to wait until my chicks were a bit older, then I hatched more chicks, then more, then more! You get the idea. I wanted to be sure and include everyone, since the virus is shed for about a week after vaccination, and I just never could do that. Looks like I got lucky though (knock on wood) as the mosquito season is almost over. I have it though, and if I see the first sign of it, I'm ready! It's a slow moving virus, so I'll still have time to vaccinate any not showing signs.
Anyway, hope it's nothing and your chicks are fine and dandy.