If you are operating in one-arm mode, it may be a feature interaction with SNAT. Since SNAT is never needed in one-arm situations, try turning this feature off in System Configuration > Miscellaneous Options > SNAT Control. This controls whether LoadMaster NATs connections using it as a default gateway. This can be necessary in two-armed configurations but it generally presents a problem in one-arm deployments.
If you are operating in two-arm mode, you may need to set up routing to use LoadMaster to reach the server subnet. Alternatively you can use LoadMaster to forward traffic for the desired ports using a virtual service for each server.