NetMetal 5shp tripple low wifi throughput

There is a Net Metal 5SHPN triple (RB921UAGS-5SHPacT-NM) with cheap antennas, connected to hap ax2 via Lan 100Mbps. When connecting the client via wifi to hap ax2, the speed is about 200 Mbps (speedtest.com ), when connected to Net Metal 5SHPN triple, the speed is only 50 Mbps. I tried the channel frequency settings both manually and automatically, I changed the channel width from 20 Mhz to 80 Mhz, there is no increase. What could be the problem ?