What decides the content of mouseover graphs in the Device Overview screen?

Hi,
I have a combination of linux, windows, freebsd machines and 1 esxi box it all runs on monitored. When I mouseover the hosts, the number and type of graphs displayed in the popup vary between the types of hosts somewhat.

What I see when I mouseover:
linux machine - processor usage, memory usage, storage usage
windows machine - traffic, cpu usage, memory usage
freebsd machine - only 2 graphs - processor usage, memory usage
esxi machine - only 1 graph - device traffic

When I mouseover the esxi machine in the syslog dashboard widget, it displays 2 graphs (processor usage, memory usage), but the memory usage graph is empty and titled Error drawing graph. When I view the esxi machine details the memory graph is present and correctly drawn.

Is this customizable in any way or is there any configuration change on the monitored machines I can do to effect something like this:
add traffic graph and remove storage graph on my openwrt router
add processor and memory graph to the esxi host
etc…