Hum coming from Turntable

Try this. Gently move your cart wires a bit with your finger when everything is turned on and the tone arm is “home”. See if that changes anything. I had ground issues for quite awhile and found that I had to have anything the turntable was connected to plugged into a single outlet via a power block of some sort. I currently use a Shunyata hydra which is great. Overall though, the ground issues I had related to the phono stage and it’s position relative to the tone arm. 

What happens when you disconnect the cartridge at the cartridge, first with clips isolated then with both channels shorted to their ground leads?

Try different cartridges to see if they are all affected similarly. Try grounding yourself and moving your cupped hand around the cartridge.
If the hum changes the cartridge is not well shielded.

The tonearm ground should be connected to the turntable which in turn should be connected to the phono stage. You can try floating the ground on your preamp with a cheater. I have an IEC power cord that has had the ground plug pulled off the male end I use for such occasions.