If your neptune is running below 3.4TH you need to put better thermal grease on the boxes that are running slow. Check the dies and see which ones are not working. I use a amp tester to see which Neptunes are pulling low amps.
1) Start with your Neptune that is running slow. Unscrew the 6 torx screws on the case and remove the lid.
2) Unscrew the 3 torx screws holding down the heatsink.
3) Remove the crap thermal grease with a paper towel.
4) Apply some Diamond IC Thermal Grease
Put the heatsink back on and spread it around and then screw everything back together.
Out of 50 Neptune boxes I have had to do this on 12 of them. They are all working perfectly now.