I've been feeding PupCorn treats for years with no problems. Clover is weirdly obsessed with them.
It sounds like an allergy, but more likely environmental or food related than the occasional treat. Especially true if ears are plucked and cleaned, making it more likely a systemic itchy reaction than and ear-specific problem.
A professional handler I know swears by fish-based dog food for ear problems. She has some top-winning English Setters she feeds Pro Plan sensitive skin/stomach and has had chronic ear infection dogs clear right up when they went to fish based food. Clover eats fish dog food and has never had any ear problems, though honestly not sure if it's related or not.
What food are you feeding? Has this only been an issue now, during pollen season? It wouldn't hurt to take them off the treats an see what happens, but I would explore other allergy issues at the same time.
Before Rico I had a beloved blue Shar Pei for 11 years. From the time I got her at 8 weeks, she had chronic ear infections. I spent literally, more $200 a month at the vets for cleanings, treatments, medicines. After almost 2 years the vet declared stenotic ear canals and recommend ablation surgery on each year at a price of 2K per ear.
Husband researched and found a vet practice that only did allergies, eyes and ears about 2 hours from our house. We made an appointment. The initial exam was 375$. The wonderful vet confirmed stenoic canals BUT said, "Before surgery try a prescriptive ultra low allergan food. In my practice 90% of chronic ear infections are allergic reactions. I don't sell the food but your local vet probably does. Let's try that for 3 months."
We drove home to our vets office and asked the receptionist for Science Diet Ultra ZD as recommended. As she went to get it the vet walked out and said, "Is this for Razz?" We said yes and we thought we'd try it as she was scratching. He said, "Oh yeah and it might help her ears too."
After 3 days, Razz stopped digging at her ears. We were able to stop the saily cleaning and meds. After a few weeks she never again had those gunky black ears or itching. She died nine years later of cancer, but her ears were as pink as a puppy's.
Needless to say, we dropped that vet. The wasted mo'ney was one issue, but the suffering that lovely dog endured for 2 years was criminal. Thank goodness we didn't put her and our checkbook through the double surgery.