I'm guessing again, but I assume you tried this?
sum += data;
sum2+= data2;
delay(1000);
data = analogRead(sensorOne); // read sensorOne value.
data2 = analogRead(sensorTwo); // read sensorTwo value.
}
That might have improved matters, but there is still a possible flaw: If the readings are still too low, you won't turn anything off and things will continue to get moister and hotter. There are some delays in your loop at the top. If one of the data values rises above voltage before the next iteration, there is no code path that will ever turn things off.