As Paul suggests, try to roll off this noise with bypass caps.
In addition, I could suggest a filtered supply (filtered to the Hz of noise + harmonics), drain caps at the load ends - drain to shields, create an Isolated grounding setup, and finally an Isolated power system.
Be sure all the shields and other grounding items are star connected at one point ONLY!!! Otherwise you will never get rid of the loop currents, and end up adding more noise to your system than removing.
Drive everything to Earth Ground at the same single star point.
If you plan to include AC Line filters, or other Line "PI" filters, connect the stuff driven to ground via an Isolated Grounding Conductor, which also terminates to the star point.
Looks like you need to place Low Pass filters at each crucial point, plus drain each circuit's conductor to ground at each crucial point, via a ceramic cap connected to the shield. One per conductor is needed.
Let us know the progress!
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!