I'd actually go a little better than soapy water and use an actual
leak detector spray. You'll spot leaks instantly with this stuff, and it's far cheaper than a CO2 tank refill.
I would also guess it's a keg since you just started using keg lube and also moved all your kegs around. You probably had a reasonably tight seal which got loose when you moved things around.
Get the spray, lube up all your posts and O-rings (don't forget the keg lid o-ring), and turn on your gas before you hook up any of your kegs.
Do a leak check on your regulator(s), the barbs where your gas line connects to your regulator(s), and the barbs where your gas line connects to you disconnects.
Once you're satisfied with that, start hooking kegs up one at a time, and check for leaks around each post and the keg lid. Keep going until you find the leak (or you're satisfied that the leak is gone).
Not sure if you're using new kegs or old kegs, but either way it's a good idea to get a supply of all the o-rings and be prepared to switch them out regularly. They're really cheap, so if you even suspect one is bad, toss it.
This post gives you all the Mcmaster-Carr links and part numbers. Very cheap. A lot of folks use the red silicone ones on the gas side as they're better and will hopefully help prevent a leak where it's just gas and thus less obvious, and then they use the cheaper rubber ones on the liquid side with the thought that if it's a liquid leak the cheap o-ring will make it really obvious.
Hope that helps, and good luck! I was pretty anal about checking for and locking down all leaks when I got my kegging setup going (and again when I setup a force carbing setup out in the garage), and it's definitely a piece of mind knowing you're not going to come home to empty tanks or freezers full of beer!