Do the chicks have a known bacteria infection that has been diagnosed?
If not, don't medicate for an unknown problem. That is how superbugs are created.
It is very unlikely for a chick that young in a brooder to have a bacterial infection.
In the US alone there are 2.8 million human infections...
Questions for you. Age of chicks, number of chicks, size of brooder and what temperature is 'in range'?
Is there just a warm spot and the rest of the brooder cool?