Harold,
More info about the service(s) please...
That many GECs would indicate possibly that each panel has a main bonding jumper and a GEC connection?? Is there a Main for the building? Each unit?
I recently saw an installation at a 4 story elderly housing with 6 metering closets. Each closet in the complex had it's own service conductors, main switch, breakers for apartment subpanels and GEC connection. Add one for the 'house' panel and that made 7 GECs clamped onto the incoming copper water service.
Return current on a GEC that is bonded to the neutral is not at all uncommon. 1-2 amps is quite low.
The fire may be completely unrelated except for there being someone in the closet moving 'stuff' around and blocking the heater discharge.
Tell us more!! J.
