My thoughts are that it may well be the wire lengths you are using.
Are the wires all properly shielded ?
Consider giving items that are long way from the Arduino thier own power supply.
If it seems random they may be picking up electrical noise and think its actually a signal.
EDIT if you give them thier own PSU don't forget to keep a common ground back to the Arduino as that's quite important.
Consider also putting the Arduino in a metal box too.