I believe I discovered a bug for the Arduino Blynk library v 0.5.3 using Arduino 1.8.5.
I modified an existing file (previously uploaded April 28, 2018), compiled and OTA uploaded it to an ESP 8266 Node MCU. All of the data from a BMP 280, MQ2 and HC-SR04 sent to my iPad and iPhone on the Blynk started reading zero.
I changed the Blynk library from 0.5.3 to 0.5.2 and the correct data was sent to my devices. I repeated changing the Blynk library versions to confirm. The Blynk app on my iPad and iPhone is v 2.21.0(2).
One interesting item of note is the correct data was sent to ThingSpeak while the file was using v 0.5.3.