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Thank you for the responses! It does appear that the number of errors for "au" is decreasing and the tool showed me that things are set up properly. I will update if I see the decreasing errors trend reverse.

HI! As the previous answer says, you must always present all the countries and languages (or just languages) related hreflang annotations as many are the multicountry/multilingual version of your site. So your own first question (My question is, do both of these tags need to be on both the Spanish and English version of the page?) is the correct answer.