I don't know what the spots might be, but I'd move them to a Q/T immediately. If it's bacterial, you don't want it spreading if you can stop it.
How long have you had the tetras? Have you introduced any new fish to the tank recently? Any other fish with signs of illness within the last month or so?
How long have you had the tetras? Have you introduced any new fish to the tank recently? Any other fish with signs of illness within the last month or so?