Hello and welcome to BYC!Did anyone figure out what was happening to these chicks? I have a 4-5 day old that's doing the same thing.
Start with your temperature. Make sure it is not too high or too low. If you suspect illness, error on the side of caution and keep it up a bit around 95 degrees Fahrenheit. I like to start healthy chicks at 90 degrees. But sick birds need a bit higher heat. Get a VERY reliable thermometer and lay it directly beneath the heat source on the floor so you know exactly what the temp is. If it is too hot, they will over heat, pant, breathe heavy and can die. So make sure you know the exact correct temp.
Make sure there are no drafts in your brooder...so solid walls and floors. Do not cover the lid with anything but a screen or wire for good heat and oxygen exchange.
Keep the heat off on one side, the food and water on the other. This gives them the ability to adjust their temperature if they are cooler or warmer, they can find a perfect spot in the brooder. 1/2 to 1 square foot per chick.
Next...are these dry sneezes or wet sneezes? Dry ones are usually due to the dander the chicks are putting out as they are starting to molt out their fuzz. So lots and lots of dander will be filling the air for a few months until the molt into their final adult feathers. Bedding, especially wood shavings are dusty. These can cause sneezing as well.
If you have the correct temp in your brooder, no drafts and they are still wet sneezing up a storm and not eating or drinking, you no doubt have a bacterial infection going on in the brooder. I would get them started on some antibiotics of some sort and quick. Babies die fast. Some Duramycin or Sulfadimethoxine will help with most respiratory infections.
If these are dry sneezes, I wouldn't do anything. Chicks dry sneeze in the brooder quite often.
Keep us posted!
