If you can find your way onto the console of the blade server affected, you should be able to find its IP address, and then in turn log onto that with the vSphere Client and see what's going on.
If the console is unresponsive, right away you know it's crashed. If your client won't connect, right away you know it's crashed. If you connect and see all the storage offline - that's the most common reason for all VMs to go offline.
Let's see what you can see.