I have a mixed batch of ages in a brooder outside w/ a heat lamp. They are 3 wks old and 1 wk old. They have been presenting w/a respiratory infection starting yesterday. Can I add antibiotic (oxytetracycline and gallimycin) to their quart waterer? I worry the 1 wk olds are too young for it. (P.S. I don't want to start a heated debate whether to use antibiotics at all on chickens, I know some people don't under any circumstance and will cull the sick, but these are pets and it's getting uncharacteristically hot during the day for March here - they aren't needing the heat lamp during the day. I had 1 that had difficulty breathing yesterday and just want make them comfortable). Thanks.