3-site inter-office GRE bridge for 2 VLAN's over Juniper SRX-220 JunOS

I want to link 3 offices via a GRE bridge across 3 dedicated Juniper SRX-220's, each tied to public static IP's. We tried MPLS, but couldn't get it to transfer traffic. We tried Cisco ISR4321's, but they had a speed limitation of 50 or 100Mbps, depending on licensing. I want the tunnel to pass/route 2 subnets, one management and one traffic, each on different VLAN's. I can't change the VLAN's. I can attach a network diagram if that helps.