discovery.seed_hosts in elasticsearch AWS EC2 with ELB

I have EC2 instances under an ELB. Whenever a new instance is started an ip address is assigned dynamically.

I have added the ELB DNS name, but it is referring the ip addresses from Network Interfaces tagged to the ELB. But I need to add the ec2 instance ip address.

So how do I add the new ip address in discovery.seed_hosts in elasticsearch without manual intervention?

Note:- I am looking for a way other than ec2 discovery plugin