Got to Settings-System-Licensing. Click on Usage Report button,select Previous 30 days tab and from the Split by tab Split by Host from the dropdown. This may show the offending host if its not lumped in with "Other".
There's also the SoS app to look at for current indexing throughput, or the new-in-6.2 distributed management console that has the same info in a prettier wrapping. License Usage Report will be easiest though because it's built-in.