Unless you know what the exact sickness is, throwing meds at it may not help if it isn't the right med for the sickness. I'm not knowledgable enough about meds to say if the tetracycline is the answer. Perhaps someone else will know what it treats.
I don't know that it is anything to worry about Cari. How soon are you planning on processing them? I am always very hesitant about giving my meaties any meds, but then I always have more than 6, so if I lose one, it's not the end of the world. If they don't show any additional symptoms or...