Every spring one or two of my cats pick up ear mites. I get them treated with Tresaderm. They aren't outside cats, only occassionally. It doesn't get to be too bad of an infestation. But why the ear mite problem every spring?
Ear mites are transmitted by other cats. maybe your cats are exposed to other cats with mites. there are more cats out roaming around in the spring. I recommend treating with tresaderm. vetcare