we not able to give medical advice and happy your working with a vet. You can ask if this is a food , or environment reaction is it bacterial or yeast base situation .. I had the same situation with two of my gsd's get drops for their ears and it would clear right up and even with extended use before we weened them off it would be back full force with in 3 weeks. Reading B Naturals news letters was helpful at the time as one source of information.