If you have possession you have no unlawful detainer case. UD is a case for possession only. You can dismiss or covert the case to limited jurisdiction for money damages only. Regardless you need to amend to fix the pleadings. And because they answered you need to apply for leave of court. Absurd because you have possession!
So dismiss the ud and file a small claims action for damages (if you have any).
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I agree with my colleague's excellent answer, but I respond to add a caveat. If you do not know where your former tenants are now living, it may be easier to amend the pleading than dismiss the complaint, locate the tenants and re-serve them for the small claims action.
The false claim that the tenant cleaned the property after move-out inspection is a question of fact to be addressed when you seek damages or they seek to recover their security deposit. If you file in small claims, you can sue for unpaid rent, the cost of repairing non-wear and tear damage to the property and cleaning fees.