I would run some searches from the search head to make sure indexers are returning results.
Like -> index=* | dedup sourcetype, splunk_server | table sourcetype, splunk_server
Make sure the splunk_server field mentions all the indexers that you have.
Also, run search -> index=_internal -> in all-time real-time and check for the splunk_server field to make sure that all the indexers are ingesting the new data coming to Splunk as expected.