I would suggest having a vet look at, clean out, and maybe culture the ear. The mites could be gone but a yeast infection might now be resident in one ear. Might be the pain is from a weed seed stuck down inside causing an infection.
Often repeat ear issues go along with allergies or thyroid problems too.
Or if you only want home treatments you can see if this will help however its not to be used if the ear drum is punctured so I still suggest vet review of the problem
http://qtpawzpoodles.tripod.com/earcleaner.html
Hope this helps you!
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