I just moved into a new appartment, and I'm having a bit of a problem
with ground hum.
My amps are NOISEY as hell now!
Surprisingly, my tube amp isin't AS bad.
But I have a tiny little solid sate (Marshall MG10) that I use
simply to practice on, and WOW, is it ever noisey!
Its DEFINITLEY a ground hum issue, because I have never had this
problem in my previous appartment, and I've tried switching cables, guitars, etc...
And it seems to depend on where I am standing in the room.
Needless to say, quite irritating.
Any suggestions?

Try a different room/outlet.
Be aware of:
Dimmers.
Tube lights.
Wireless devices.
good luck