It can be tricky especially when they cannot tell you what is going on. In any case, some of what you described is likely hyperpigmentation which is a skin darkening reaction to chronic irritation. Though with what you are removing, I suspect its an overgrowth/build up of yeast. This can occur in some dogs that have underlying allergies or immune suppression, so we do want to keep a close eye on Kiara as we try to reduce this build up for her and prevent recurrence.
For that, you can wash these areas a few times daily with dilute chlorohexidine as that can reduce yeast load. There are also OTC wipes/shampoos (ie MalaKet, Malaseb) that work well for keeping the yeast levels down. Most vets carry them or Amazon do as well. Finally, just in case she has any irritation or if there is a concern of an underlying allergy, you can also consider an antihistamine at this stage. Most commonly we use Benadryl/Diphenhydramine (0.5-2 mg per pound of their body weight every 8-12 hours) to reduce allergic irritation. We like to keep the dose low, as it can cause drowsiness (just like people). And of course, this medication shouldn't be used if your wee one has any pre-existing conditions or is on any other medication without speaking to your vet first. But again this material looks like yeast based discharge, so we can use the above topical treatments for her. Of course, if it were all over or she didn't settle with the above, then we'd want her local vet to swab this for culture +/- provide systemic/oral treatment so we can treat from the inside out for her.
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