You could take the 328 chip out of the working one and put it in each of the other Arduinos to see if that revives them. Check for proper 5V on each board before putting the good 328 in and make sure nothing else is connected. If the good 328 makes the other boards work, then it may be a corrupt bootloader on the bad ones. You could then use the good 328 to re-burn the bootloader on the sick ones.