Deadman alert fails for some hosts


I have a pool of servers and I am gathering metrics from then and putting into an InfluxDB.
Now I created a deadman alert on chronograf that sends me alerts by email when one of my servers fail

but I think something is wrong

I always receive alerts about one of my servers that’s working fine
On the other hand, I’m not receiving alerts about some others servers when they’re down

What I must to do ?

My config