If you have recurrent ear infections, they might need to be cultured and tested for sensitivity. They send a sample off to a lab, grow it out, and see what drugs, if any still work on it. It could be that the medicine simply isn't healing them.
I would also consider using Zymox Otic regularly for a while on a dog with this issue. It's an OTC ear treatment that has an enzyme that prevents microbial overgrowth. It's easy to use (no ear cleaning), and painless. The kind with hydrocortosone relieves pain and itching almost instantly too -- but they also make it without HC. I keep a big bottle around. The way I use it is to do a week-long course at the first sign
of an ear issue in problem-prone dogs (meaning as soon as the dog starts batting at its ears)...and it almost always eliminates the issue without the need for vet-prescribed meds:
You can read about how it works here:
Pet Ear Health | Zymox Ear Treatments - zymox.net
People on the Internet also love to say yeast is caused by eating carbs, but the science doens't support it -- it's a myth that's been repeated so often that people believe it's truth. The only problem is that it's not true:
be associated with allergies because inflamed skin is more susceptible to infection by staph and yeast. But food allergies are far less likely than most people think.
As for real food allergies, PROTEIN is much more likely to cause an allergy than GRAIN. You'd never know that from the grain-free marketing hype though. So if you're looking for a suspect and feeding a lamb-based food, lamb would be my first suspect. You can try getting the dog off lamb for at least 6 weeks. (FWIW, my dad feeds Purina One, and he rotates all the "types" in the line...except lamb! That one gives his very sensitive dog diarrhea. It is different enough from the rest of the Puriana One line in his experience that he just doesn't buy it.)
I've fed a lot of Kirkland/Diamond Naturals
/4 Health Chicken and Rice to foster dogs, as that's what our rescue buys (they're all basically the same, just sold under different labels). That particular Diamond-made food feeds out great to dogs who don't have allergies to its ingredients! It's a very good "budget" food at $28 per 40 pounds at Costco. There are better foods out there, but not at this price! (Note that this isn't the "regular" Diamond food -- it's the Diamond Naturals line).
Fromm Classic is definitely worth looking at. It's chicken-based. It's significantly less expensive than Four Star, with about the same protein and calories (and no peas!). It's their lowest cost food, but the ingredients are still quite nice!
Victor should also be on your radar. Their entry-level foods are also in the same price range, and many dogs do well on it.
For allergy dogs, the rescue buys Wellness Simple because we've had much better success with it than with other limited ingredient foods. I don't know why, but they more of them react better on it than the other brands we've tried.
If you're giving her chicken bits as treats, you can try feeding a chicken-based food, and only doing chicken-based stuff for a few months, and see if it makes any difference. You need to pick ONE type of protein, though, and stick with it for 6-8 weeks, without mixing beef/chicken/fish/etc. if you're trying to see if there's a food allergy!
There are also a small number of dogs that just don't do well on kibble. While two of mine do great on Fromm Four Star, the third one is such a mess with genuine allergies that we can find no kibble that works for him. He has to eat a fresher alternative diet. You're a long way from that though. Hopefully something simpler will solve your dogs problems!