Heaters (especially the cheap ones) don't actually heat to the temperatue that you set them to, the numbers on them are just a guideline just set the temperatue with a good thermometer in the tank and disregard what the heater says, you can calibrate some heaters I am not sure about the sunsun ones. I haven't really had much luck with the stick on thermometers they don't appear very accurate, also your tank only holds around 130L so you only really need 1 150W heater in there so I would only run one of the 200W ones.