1519P06 is the latest from stable versions. To be honest, I have checked our internal s/w repository and do not see anything newer for this model - no betas, no hotpatches... And it is more than a year old, so it must be stable enough for production usage.
I have seen it many times before when perfectly working old equipment breaks on reboot. Just a reboot, no updates, nothing fancy. It is a specific of electronic equipment that some modules that already have defect just die on power cycle. And some 1910 are quite old, especially if we take into account that many switches work in sub-optimal environmental conditions - humidity, temperature etc. etc. Maybe before proceeding with an upgrade you can perform a reboot to verify that the device has potential to survive the upgrade...
Taking all this into account I would not jump into conclusions that the upgrade was the trigger. Even if it was, it could be a defective flash memory that currupted newly uploaded image. But in this case console ports would work and you would see certain error messages. But if after upgrade console ports go down and switches do not light up port LEDs on connection, I would definitely suspect a hardware issue rather that a software one. Another point - if that would be an incompatibility between releases, why 3 of your switches were successfully upgraded and ? Of course, this point makes sense if initial s/w versions before the upgrade were the same on working and non-working devices.
I am not excluding a possibility of an unkown incompatibility problem that you may hit, just one thing does not fit into this scheme - dead console ports. Normally you should see at least a POST test result on a bootup. And if there is an issue with s/w image, the bootrom should inform you that the image has failed to load. BTW, try the following test - leave the console connected with terminal client open and reboot the switch. Let's see if you get a POST test results at least.