Juniper EX DHCP Relay

Hello,

I am trying to get DHCP relay to work with multiple subnets on an EX4200 switch.  

set interfaces vlan unit 12 family inet address 192.16.108/25 primary
set interfaces vlan unit 12 family inet address 172.22.18.1/26
set interfaces vlan unit 12 family inet address 192.16.110.129/26

set forwarding-options helpers bootp interface vlan.12 server 192.168.108.101
set forwarding-options helpers bootp interface vlan.12 server 192.168.108.102

DHCP works, but once all the IP's in the 192.16.108/25 range get used, it does not start dishing out from the next range like it does with Cisco.  What am I missing?

Also, these IP' were edited.   In real life network they are public ip addresses, and so I can not simply just create a larger subnet. 

Thanks!