The lease terms can not be unilaterally changed in the middle of the tenancy. When the tenancy is up for renewal, however either of the parties may choose not to renew the tenancy, or to change the terms. If the tenancy is month to month, the landlord may terminate the tenancy pursuant to 83.57 F.S. by providing 15 days notice. The notice must be served according to 83.56(4) by mailing or personal delivery, of if the tenant is absent from the premises, by posting. In said notice, the landlord may propose new terms for the next monthly tenancy. The tenant then has the choice to remain, accepting the new terms, or to reject the new terms by vacating at the end of the monthly rental period.
If the notice is not provided, is defective, or not properly served, then the lease is not terminated and no changes have been made.
Here is a form that you can use to change the lease terms.