We all need more info than what you have provided.
Are the VMs on a single physical host or multiple physical hosts in a cluster?
What type of storage are the VMs sitting on? Is it external Tier 1 or 2 storage or internal SSD or NVMe disk?
What is the MTU of the NIC/s in the OS and/or physical switch interfaces?
What vNIC driver are you using? vmxnet3 or e1000?
What are your TCP/IP settings? LRO, TSO, LSO, Ring Buffer size, etc. You could be dropping receive/transmit packets in/out of the OS. Your ring buffers probably need to be increased to 4096 if you are trying to move a large amount of data.