Legal Question in Landlord & Tenant Law in Maryland

It is not clear which tenant is threatening to sue. Is the first tenant claiming the deductions were inappropriate or the second seeking reimbursement?

The answer is governed both by the law and by your lease. Most leases govern who has responsibility for what and allow landlords to deduct damages from a security deposit. The law usually allows these deductions so long as they are properly documented and made in the appropriate time frame. (There are certain limitations: for instance a landlord can charge for cleaning but cannot deduct for ordinary wear & tear)

Ordinarily landlords do not have to "pay back" monies spent to fix or clean whatever a tenant damaged themselves. On the other hand, ordinarily landlords do have to deliver property in good condition so that if the new tenant(s) cleaned up after the old and paid to get the property to move in condition then it is reasonable for them to expect reimbursement.

While I hope the general legal information above helps, it does not substitute for specific legal advice. The particular facts of your situation may affect how the law applies to you.