Under the laws of all states in this country, a tenant can legally repair and deduct future rent for repairs that the landlord fails to make in a reasaonable amount of time pertaining to habitability and/or safety issues.
The issue concerning the toilet depends upon whether you were given timely notice of the problem with it soon after it overflowed and if so, did you make a hasty effort to get the situation resolved?
If you were not given an opportunity to fix the toilet in a reasonable amount of time then it was wrong of the tenants to hire a third person to make the repairs and to have deducted the costs from the following month's rent.
The Answer(s) provided above are for general information only. The attorney providing the answer was not serving as the attorney for the person submitting the question or in any attorney-client relationship with such person. Laws may vary from state to state, and sometimes change. Tiny variations in the facts, or a fact not set forth in a question, often can change a legal outcome or an attorney's conclusion. Although AttorneyPages.com has verified the attorney was admitted to practice law in at least one jurisdiction, he or she may not be authorized to practice law in the jurisdiction referred to in the question, nor is he or she necessarily experienced in the area of the law involved. Unlike the information in the Answer(s) above, upon which you should NOT rely, for personal advice you can rely upon we suggest you go to AttorneyPages.com
and retain an attorney to represent you.