I agree, ear mites. There's multiple ways of treating them, the most common seems to be some sort of oil, be it mineral oil, olive oil, coconut oil, etc. as it suffocates the mites but you have to reapply each day and it is also recommended to work it in a little by massaging the ear at the base.
My rabbits always hated me when I did that route, and I finally got Ivermectin (pour on for cattle) and tried a single drop in each ear and cleared it right up in a few days without ever needing to reapply. Ivermectin is a parasiticide, so not the most natural route but for my critters I much prefer it due to how fast it clears up and I don't have to mess with their ears and one single drop doesn't bother them.
Good luck with whatever you choose!