After I received deposit I discover criminal background.

[Luz F.]

After meeting with many prospective tenants I decide on a middle age couple and their son. When I said I would run a credit check he let me know about troubles with IRS and child support but it seems to be way in the past. So I accepted a $900 deposit pending credit/background check. I almost did not even check the wife who I know because has been the manager at a local restaurant for the last eight years. Anyway, she was arrested in December 07 for possession of cocaine and driving with tags that did not belong to the vehicle. She was sent to jail for one day and now is on probation.
Do I have to explain why I am returning their money? Do I have to put it in writing or just tell them? I live in Florida.
Thanks,
Luz