@Sai Gutta You should not edit the size of existing host pool members as all Host pool members need to be the same size. If you need to amend the size its easier just to create a new host pool.
However, If you have a small number of hosts you can manually re-size them from the Azure portal, but they need to be powered down, see my screenshot of how to do this.
But as I said, please ensure that ALL the members in a host pool are the same size.
