Rattling sounding chicken

[Kabber]

HI....My Rhode Island Red hen has been making rattling/gurgling sounds the last two days. I went today and put Oxy Tetra A in their water bowls......probably should have isolated the one hen but gave it all of my 21 hens just in case. Will this hurt the other hens ? Does anyone know how long to give it to them for and how many days to I have to wait until we can eat the eggs again...What a waste of eggs....having to throw them out......Would the eggs really hurt us ..it's a very low dose of antibiotcs....

Any advise will help...Thanks,

Mama Chick Kab