I can hep with that
Reduce the height of the stems by half, and cut off yellowing leaves and dead flower heads. Put the pots in an unheated spare room or in a cold greenhouse. The plants like City fans will be exhausted after their summer long activity outdoors and should not be treated as house plants to be coaxed into flowering. They need a rest and on no account should they be kept warm. Do not feed them, and water only when it is essential to stop the leaves from flagging.