More info would be good.
Diet, age, type of bedding, any new introduction, weather and so on.
Very young chicks sometimes gasp because of hatching or other fluids getting down the wrong tube when hatching. Sometimes they have issues from the start and result in a failure to thrive.
Older chicks could have aspirated something.
If they are older, separate what you think is sick, if it acts sick.
As for antibiotics, they aren't a cure all, all and giving them cocktails for something that may even be viral is just going to make the antibiotics useless on both the birds when they really need it, such as injury, and yourself, when you need it. Good and bad bacteria can pick up resistance genes, and share them with each other, be they be on the chicks or on your skin.
So if you choose to use an antibiotic, use wisely and do a full course, as viral issues will just keep on going, and bacteria can become resistant with just one use.