You need to use a cluster-aware file system - plain vanilla NTFS, that I'm pretty sure you're using, isn't one.
The issue is that whenever two boxes share the same data something needs to manage the locking so that one server doesn't overwrite another's data and cause corruption.
In a NAS environment the NAS protocols themselves (say NFS, CIFS/SMB etc.) and the NAS controllers inherently manage this locking process. In a SAN environment (FC/FCoE, iSCSI) the servers themselves have to manage this process, meaning it's actually the file system on those boxes that do this job.
Now I have to tell you right away that what you've done already will have very significantly corrupted the volumes you've already made, I have to say that so you can understand the impact that has on your project and timelines.
Now you need to figure out a way forward by selecting a cluster-aware filesystem. There are a number of these, in a VMWare world their default filesystem (VMFS) is cluster aware, as is Oracle's OCFS/OCFS2 in their linux world and there are others in the linux space too.
For Windows there's two options I'm aware of, the one I use is Symantec's 'Veritas Storage Foundation for Windows' - not only does it allow you to create an NTFS-compliant clustered file system but it'll also add in some multi-pathing options too - that's why I use it, it's far from free however.
What you can also use is MS's own cluster service, this can be a bit daunting at first to configure but essentially it adds a new service to your Windows servers that handles the block-level locking that's needed, you'll have to implement the multipathing separately using MS's MPIO mechanism but this scenario is at least included in most versions of Windows Server. In fact this is the recommended method for setting up older versions of MSSQL, so there's lots of documentation around to help with that.
So to summarise, this stuff doesn't just work on its own, you have definitely killed your file system, hopefully that's not an issue - and you need to pick a way forward and deploy that.