Antibiotics are usually quite safe, as long as you use the right dosage. However, I wouldn't give your chickens antibiotics unless they're sick--that will only lead to a less-healthy, bacteria free digestive tract and possibly antibiotic resistant bacteria.
Thanks for all the replies. They are just pale except for 1 of the hens. My wife is overly concerned. 3 month ago one was very sick I used it to help the 1 . After 3 days she was fine I will stop use. Thanks
Being pale may be related to mites or internal parasites. I wouldn't use antibiotic's unless there are other obvious signs of some illness. You live in a climate that is conducive to a high parasite load, have you tried deworming your birds? And check them over very carefully for mites or lice. When you do that you can also check them over and see if they feel thin.
What were the symptoms of the one that was sick three months ago?
If you can, take a poop sample to the a vet and have them check it for worms. If you can't do that, just go ahead and worm them with Safeguard or Valbazen. Also check them very closely for mites and lice.
When using antibiotics, what is the safest wait time for using the eggs? Some warnings on antibiotic packaging says not to use on chickens providing food. Does that mean that if you use the antibiotic, you can never again eat the eggs?