one of VM in the datastore must have a very hight write workload. I think you can identify this vm from vmware site. Some 3rd party monitor tools can help you. Like Quest_Foglight-for-Virtualization-Free-Edition-for-VMware
is it block access right? (mean lun, not nfs). You can't decide which vm have a high workload in a lun. lun is a huge file on storage site. we can't see which vm has a high utilization in that lun. I think, if you want tı figure out this issue, you have to analyze this workload from vmware site.
And If you want to see snapshot size, KB change ratio, and RteKB/Hour data, you can use "snap delta" command from storage cli.