Yes common problem once coolant leaks it leaks down in the engine V and that soaks the sensors. Again a typical design flaw from our Italian Friends.
Yes both sensors should be changed when doing the job. One other thing worth considering doing at the same time are the 4 short water pipes as these OEM parts are simply poor quality and will perish in the end. Well worth fitting a much more durable silicon pipe in place.
part no 585089700 for the Knock sensors.
The 4 pipes I refer to are in the picture (fitted with more durable blue silicon hose)