I have two 18 year old cats that I would like to treat. I do not know of any specific ailments but I suspect one may have bladder/kidney issues. Any suggestion?

I would indeed start with detoxing and also normalize bodyfunctions. When you search for "normal" you will get sets that work on the organs and bodysystems.
Keep an eye on them when you are running the frequencies, because animals can respond strongly to frequencies. I would use low amplitude.

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