You don’t ned to do this. One timer object can handle up to 16 timers. so just stick with…
BlynkTimer timer;
you’ve gone from taking a reading every 5 seconds to taking two every 10 milliseconds and Blynk can’t cope with that…
You should probably do this:
timer.setInterval(5000L, waterLevel);
delay(500);
timer.setInterval(5000L, foodLevel);
The delay between the two timers means that they start half a second apart from each other.
If you want more info on timers you should read this (although it’s probably best reserved for when you’re having a sleepless night and counting sheep isn’t working)…
Pete.