@Jon FletcherYou have a tenant problem and the mice are a symptom.

Your policy can require, for example, that you are provided a current Veterinarian's report on the health of the animal; a letter or form from a "reliable" source such as a local medical or social professional verifying that the tenant has a "qualified" disability, and that the animal performs a specific task, or alleviates a symptom related to that qualified disability; tenant must clean up after the animal in common areas; no offensive odors can emanate from tenants residence; and both the vet report and verification of tenant's need must be updated annually. 

Does the animal perform a task, provide a service, or alleviate symptoms related to the disability?

Be firm in requiring proper documentation, but there's not much you can do after than until you can demonstrate that other tenants are negatively affected (ie allergic and having symptoms) or the animals are doing damage to the apartment

They just started feeling sick for a few days, then finally a friend recognized the symptoms and they had the fire department over.

You can go online type in what the "symptoms" are but don't tell them you know what is really going on...let them tell you.

If there's no rust or corrosion or any other sort of water damage on the electrical components then I'd say leave it be... it's leftover from a previous symptom.

The majority of the time cracking and deflection is a symptom of external issues happening around the property.

It is an animal that works, provides assistance, or performs tasks for the benefit of a person with a disability, or provides emotional support that alleviates one or more identified symptoms or effects of a person’s disability.

We used to have lots of different business cards, that we laughingly called "symptoms of our disillusionments".