Can I keep portion of security deposit?

[Carleton C.]

Backstory:

I moved out of my home, decided to rent it out, and hired a property manager. Property manager found 4 students to rent the home and they all signed one joint lease (each had co-signers as well).

Since I did not need my furniture at my new location I decided to sell it on fb marketplace for $700. On the last day before the new tenants moved in, I received a fb message from a guy requesting to purchase all of the furniture. I notice the name looked familiar and it turns out that it is one of the students who is renting my place. I told him I would just leave the furniture in place and they could pay me through Venmo. He said that he was gathering the rest of the money from the other 3 and then he’d get it to me.

Fast forward to today (11 months later) and the tenants are moving out in 2 weeks but still haven’t paid for the furniture. I’ve requested the money for the furniture multiple times and I still haven’t received it. My property manager even reached out to them about it, even though she stated (to me) she couldn’t enforce it, since it was a separate transaction from the lease agreement. Since they paid their rent on time and weren’t responding to the payment requests, I figured I would let it go until close to the end of tenancy.

Can I take the money owed out of their security deposit even though it was a separate transaction from the lease, my property manager holds the security deposit funds, and only one of the tenants requested to buy? Or should I just chalk it up as a lesson learned and move on. I have ALL written communication from the tenant where they agreed to purchase and pay, along with the attempts to collect. Originally I was just going to settle it through court if they didn’t pay, but with all of the covid stuff going on, that’s out of the question for a while.