Hi Massive. Thank you for your reply. Here's my configuration.
set routing-options static route 0.0.0.0/0 next-hop 1.1.1.1 preference 5
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS target address 8.8.8.8
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS probe-count 5
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS probe-interval 5
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS test-interval 3
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS destination-interface ge-0/0/0.0
set services rpm probe WAN-PROBE-ISP1 test GOOGLEDNS next-hop 1.1.1.1
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS target address 4.2.2.2
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS probe-count 5
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS probe-interval 5
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS test-interval 3
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS destination-interface ge-0/0/0.0
set services rpm probe WAN-PROBE-ISP1 test LEVEL3DNS next-hop 1.1.1.1
set services rpm probe WAN-PROBE-ISP1 test OPENDNS target address 208.67.222.222
set services rpm probe WAN-PROBE-ISP1 test OPENDNS probe-count 5
set services rpm probe WAN-PROBE-ISP1 test OPENDNS probe-interval 5
set services rpm probe WAN-PROBE-ISP1 test OPENDNS test-interval 3
set services rpm probe WAN-PROBE-ISP1 test OPENDNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP1 test OPENDNS destination-interface ge-0/0/0.0
set services rpm probe WAN-PROBE-ISP1 test OPENDNS next-hop 1.1.1.1
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS target address 8.8.8.8
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS probe-count 5
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS probe-interval 5
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS test-interval 3
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS destination-interface ge-0/0/1.0
set services rpm probe WAN-PROBE-ISP2 test GOOGLEDNS next-hop 2.2.2.2
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS target address 4.2.2.2
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS probe-count 5
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS probe-interval 5
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS test-interval 3
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS destination-interface ge-0/0/1.0
set services rpm probe WAN-PROBE-ISP2 test LEVEL3DNS next-hop 2.2.2.2
set services rpm probe WAN-PROBE-ISP2 test OPENDNS target address 208.67.222.222
set services rpm probe WAN-PROBE-ISP2 test OPENDNS probe-count 5
set services rpm probe WAN-PROBE-ISP2 test OPENDNS probe-interval 5
set services rpm probe WAN-PROBE-ISP2 test OPENDNS test-interval 3
set services rpm probe WAN-PROBE-ISP2 test OPENDNS thresholds successive-loss 5
set services rpm probe WAN-PROBE-ISP2 test OPENDNS destination-interface ge-0/0/1.0
set services rpm probe WAN-PROBE-ISP2 test OPENDNS next-hop 2.2.2.2
set services ip-monitoring policy DEFAULT-ROUTE-POLICY-1 match rpm-probe WAN-PROBE-ISP1
set services ip-monitoring policy DEFAULT-ROUTE-POLICY-1 then preferred-route route 0.0.0.0/0 next-hop 2.2.2.2
set services ip-monitoring policy DEFAULT-ROUTE-POLICY-1 then preferred-route route 0.0.0.0/0 preferred-metric 3