h2 = dht2.readHumidity(); // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
t2 = dht2.readTemperature(); // Read temperature as Celsius (the default) // Read temperature as Fahrenheit (isFahrenheit = true)
f2 = dht2.readTemperature(true);
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println(F("Failed to read from DHT sensor 2!"));
return;

if (isnan(h) || isnan(t) || isnan(f)) {
should be h2, t2, f2, and the same for the third DHT ;)