Updated Istio alerts.md

Author: carlosadiegosysdig

resources/istio/ALERTS.md

@@ -1,18 +1,21 @@
 # Alerts
 ## [Istio-Citadel] CSR without success
-Some of the Certificate Signing Request (CSR) were not correctly requested
+Some of the Certificate Signing Requests (CSR) were not correctly requested.
 
 ## [Istio-Pilot] Inbound listener rules conflicts
-There are some conflict with inbound listener rules
+There are some conflicts with inbound listener rules.
 
 ## [Istio-Pilot] Endpoint found in unready state
-Endpoint found in unready state
+Endpoint found in unready state.
 
 ## [Istio] Unstable requests for sidecar injections
-Sidecar injections requests has no been successfully resolved
+Sidecar injections requests are failing.
 
 ## [Istio-Envoy] High 4xx RequestError Rate
-High 4xx RequestError Rate
+4xx RequestError Rate is higher than 5%.
+
+## [Istio-Envoy] High 5xx RequestError Rate
+5xx RequestError Rate is higher than 5%.
 
 ## [Istio-Envoy] High Request Latency
-Envoy High Request Latency
+Envoy Request Latency is higher than 100ms.