The issue you are having is that the version of the firmware on your radio does not match the version of the UHD libraries that you have on your system. You need to either update your radios (uhd_image_loader) or change your version of UHD to match what the radio has. The former is the better choice in my opinion.
I think that you need to add `--init-only` to the uhd_usrp_probe command to tell if the versions line up. I seem to recall not getting the version error without it.
You likely don't need to install from source. As far as I know gr-uhd just makes use of the system UHD install. Perhaps you have two different locations that UHD is installed to? You could double check that you don't have libuhd.so in /usr/local/lib and /usr/lib at the same time. I'd suggest updating the radios to the current firmware with uhd_image_loader, power cycling them, and then trying again.