IRule to Re-load Balance

sorry if i'm not able to deliver my question regardless of persistence , here I have one TCP connection from Application server to DB server , persistence will affect new TCP connections only ) ... i have 4 DB Servers at a pool , 3 of DB Servers went Down , so all connections went to DB Server1 , when the 3 servers came back all the old connections didn't go to them & continued on Server1 ... i know that only new connections will go to them , but the idea is that i want even the old connections to be re-load balanced across all How can i achieve that ? is there an option @ GUI or Irule is needed ? ... Clearing Old Connections is a solution , Can i do that with Irule ? What command i need to use to re-load balance or reset all existing connections based on Certain Condition ?