Speed Test Loss Data on Multipl Hop

I have 3 RB1100AHx2 connected with 2 PTP Wireless Link.

Link From RA to RB if i test with mikrotik bandwidth test is 180Mbps FULL DUPLEX in TCP

Link From RB to RC if i test with mikrotik bandwidth test is 150Mbps FULL DUPLEX in TCP

Link From RA to RC if i test with mikrotik bandwidth test is 30Mbps FULL DUPLEX in TCP

There are no VLAN or VPLS in this test. The 3 Routers are connected and configurated with OSPF and MPLS routing.

In which way can i find where is the problem?

Thanks.

Check the latency between the links. TCP throughput it dependent on latency.