Fl being a right to work state should only come into play if there is a collective bargaining agreement in place. This doesn't sound like your situation. More important is Employment at Will.

"any hiring is presumed to be "at will"; that is, the employer is free to discharge individuals "for good cause, or bad cause, or no cause at all," and the employee is equally free to quit, strike, or otherwise cease work"

No cause at all is the key part of this doctrine. Firing can get ugly, you have to protect yourself. Here are 2 key factors that have worked for me.

1) Fire the person with a witness, never by yourself
2) Give no cause for the termination of employment. It's an uncomfortable discussion but your safest.

Legally you don't have to give cause. Firing for good cause can be argued, No Cause is difficult to argue. As long as you do not have an employment contract in place. Fl in the past has not been favorable to employment at will exceptions.

With this info check with an attorney.