[chromo]

"My power supply has a button next to the voltage scale, if you hold it in or tape it in the voltage reads good then?"

Maybe dumb question, but have you tested the power supply itself? Test when NOT putting out the volts on the scale. Could be under a load something is getting hot or such and the power supply is messing up, not your setup. Test the wires for the power supply close to the supply as you can. They should show your volts rather your parts are getting the volts or not if the supply is putting out the volts.

I don't have any idea what that black button is for, but it must do something to the power supply since it does not really do anything for the parts right. So if pressing the button puts out the right volts but not pressing it you lose the volts, again I think it might be in the supply.

I would run it as normall till the scale drops the volts. Just connect a digital meter to the power suppies wires. Watch the volts on the meter and the scale, see if they match and if they stay the same. Does the scale drop low but the meter still read high? Do both drop?
If the meter shows low volts also then disconnect a wire from your tank and see if the volts jump right back up again.

Also you could test the power supply under load without your tanks. Figure out your normal Volts X amps = watts. Once you know the watts your normally running connect a few car tail light bulbs and light them up awhile with the power supply. See if after about the same amount of time the volts drop on your scale as when tanking. If the volts drop of course you then know it's the supply and not your setup.