Not quite:
in setup()
timer.setInterval(3000L, sendSensor1);
then:
void sendSensor1()
{
sensors1.requestTemperatures();
Blynk.virtualWrite(1, sensors1.getTempCByIndex(0) + 6.5); //adjusted with 6.5 celsius because measuring outside of tube
int callFunction2 = timer.setTimeout(1000, sendSensor2) // TWO not ONE
}
void sendSensor2()
{
// your sensor2 code here
int callFunction3 = timer.setTimeout(1000, sendSensor3) // THREE
}