The facts posted do not suggest any justification for the demand made by the landlord. A tenant could be held liable only for the damage or loss to property beyond ordinary wear and tear. Moreover, one party to contract or agreement is not authorised to decide issues in dispute unilaterally.
However, it is the moot question is whether the issue is worth approaching the Court. You may dispute and deny the claim by the landlord through a written communication, preferably through an advocate.