HELP: Do I have a stray voltage problem? 47 volts?

Tank Info:

75 gal

10 gal in sump



Electrical Equipment:

3 hydor koralia power heads

skimmer

2 heaters

auto top off

pump for dual media reactor

return pump

moon lights

lights



Tank is 3-4 years old.



Since day one I have had fish die for no apparent reason, usually with fin rot being the only symptom before hand, sometimes with white soars (not ick) Even with supposedly hardy beginner fish such as OC clowns and cheap wrasses.



My water has always tested perfect (salifert test kits) as I do 10-12% change every week (10 gallons). My LFS has tested my water the day that I have noticed a fish gone and not found anything.



I saw a post somewhere about stray voltage so I though I would take a look.



Here are my readings...

47.3v with everything plugged in

46.8 unplugging 1st power head

45.8 unplugging 2nd power head

44.3 unplugging auto top off

43.2 unplugging 3rd power head

34.3 unplugging skimmer

33 unplugging return pump

29 unplugging heater

22.7 unplugging heater #2

16.3 unplugging media reactor pump

16.2 unplugging moon lights

11.3 unplugging blue lights

7.8 after unplugging white lights



reads 7.8v with nothing electrical plugged in.



Is this a problem or is this normal? Any help will be greatly appreciated.



EDIT:

Oh and everything runs from a single grounded power outlet that is not GFI. The previous owner of this tank put 12 electrical outlets build into the stand, the same electrical boxes and outlets you would use in the wall.