Based on the limited facts you provide, I don't see anything fraudulent about your landlords' behavior. Whether or not it violates the terms of your lease is another question.
To research if they actually own the property, you'll need to physically go down to the Property Registry for San Juan and try to look up the lineage of the property. Keep in mind that, depending on when they may have bought the property, it may not appear in their names yet at the Property Register because deeds and mortgages often take between 2 to 10 years to properly record here in PR (if they are ever properly recorded). This is because the property recording system in PR is so arcane and dysfunctional. There are some legislative initiates to modernize the system but nothing has been passed yet.
Generally speaking, people in PR do not take their rental contracts seriously. Breaches are common and often do not result in litigation (although deposits are lost, obviously).
I'm not sure why your landlord would hold your electricity deposit. Are you sure you have your own account with the electric company? Or is the account in the landlords' name?
Good luck with whatever you decide to do.
(Please note this communication does not consist of legal advice or create an attorney-client privilege. It is provided for educational purposes only.)
