ear fungus

i was feeding my guineas like normal, you know the regular routine, I noticed something on Chocco’s ear, it doesn’t make sense he seemed totally fine. What could it be and what couldve caused it? Should I seperate him from his cage mate? and is it a fungus or infection?

I just got 2 piggies a week ago from a pet store, I'm a new owner and I didn't know that you shouldn't buy piggies from stores, and now my piggie Ruby has a swollen, hard ear with dryness. I think it may be a fungus but I'm not sure. I have attached pictures of her ear after I applied some...