I think you would need to check your beats configuration file and log file to see if they're configured to send data to logstash and if that's working.
The other thing is if you have X-Pack installed (it's a plugin for Elasticsearch, Kibana, and Logstash) you could use the Monitoring feature to view these charts that show events received by Logstash and Events emitted from Logstash to Elasticsearch;
Lastly, the _cat/indices request will show you what indices are in the cluster.
Regards,
Lee