Dosages for birds are often higher than what you think.I'm giving her powder dissolved in her drinking water and a few little pieces of bread soaked in it to make sure that she's getting some in her. 1/4 tsp per gallon.
I sure hope that it's not reproductive, as she's my main breeder.
You may want to look at the link below, if you are using any of these powders, then likely you are under dosing her.
https://www.backyardchickens.com/threads/oxytetracyline-and-tetracycline-powder-doses.1022878/