It doesn't matter where you buy your thermometer and hygrometer, what brand they are, when you buy them, or how much you pay for them. If you haven't calibrated you simply CAN'T trust them to be accurate. Even the thermostat/thermometers built into incubators can be far enough off that the eggs will be killed. I can't stress often enough the absolute importance of checking your thermometers for accuracy, then checking all areas in the incubator for warm/cool spots. The time spent doing this can make the difference between a great hatch with healthy, robust chicks, and a poor hatch rate with weak or deformed chicks, or even a failed hatch.