Client route tables are fine. Their default route is through the Fortigate,Have you checked the routes, both in the L3 switch and in the clients?
Brocade only has the /24 for its virtual interface configured. Guessing I need to add a route for the other /24, next hop being the lag?
oldboy(config-vif-1)#show ip route Total number of IP routes: 1 Type Codes - B:BGP D:Connected O:OSPF R:RIP S:Static; Cost - Dist/Metric BGP Codes - i:iBGP e:eBGP OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2 Destination Gateway Port Cost Type Uptime 1 192.168.1.0/24 DIRECT ve 1 0/0 D 3h17m