I don't know about chicks that age, but my pullet (about 6 mos) was sneezing and it just got worse - to the point she was blowing bubbles out her EYES! We ended up putting antibiotics in their water and it resolved.
However, now she's sneezing again (!!) and it's only been a little over a week, so I'm worried I didn't do it long enough and may need to do another course (which I hate to do - so hard on the guts...) We've also been adding immunocharge to the water since the antibiotics, which is supposed to strengthen them plus it has probiotics in it.
Anyone who might decide to read this thread, I'd love commentary on the reoccurance of My Olive's sneezing too!