My first rule is: Report to the Landlord in a timely manner any defects, maintenance, or damage in the Tenant’s Premises, or the inside or outside common areas, so the Landlord may remedy in a timely manner and maintain a safe and comfortable environment for the enjoyment of the Tenants.

Highlight the lease section and let her know that an eviction will be on her record if she does not remedy the situation.

Each state has different laws regarding what remedies are available to landlords.

The landlord may withhold from the security deposit only such amounts as are reasonably necessary for the following reasons: (1) To remedy a tenant's default in the payment of rent due to the landlord, pursuant to the rental agreement; (2) To restore the dwelling unit to its condition at the commencement of the tenancy, ordinary wear and tear excepted; or (3) To compensate the landlord for actual damages sustained as a result of the tenant's failure to give adequate notice to terminate the tenancy pursuant to law or the rental agreement; provided that the landlord makes reasonable efforts to mitigate damages. 4.

I dont think he would have any realIstIc legal remedy

Currently there is no way the improvements have been there long enough for a prescriptive easement, you want to make sure that you remedy that before too much time has passed. 

An attorney may be needed to help remedy the situation.

The EPA has a good booklet "Mold, Moisture, and Your Home" that explains how to prevent mold and how to remedy it.  

If the Purchaser defaults at closing, the Deposit will be retained by the Vendor as it’s sole remedy. 6.

The buyer's remedy is to either get their earnest money back or sue for specific performance.