The spark plugs don't look like there's any obvious sign the engine is burning coolant.
With that said, if it's a small coolant leak into the engine, it will not show on the plugs.
Also, failure of the water jacket o-ring could make it possible it won't show on the spark plugs.
The low coolant buzzer triggering could be just because you opened the cap and compromise the cooling system - allowing some air to stay trapped and then trigger the buzzer.
I'm trying to be optimistic at this point.
The only way to tell is to drive it a significant distance and then check the coolant level to see if it significantly dropped (or puked out the overflow).
-Ted