LED Matrix Light Leakage
"For example, in the schematic below if I turn ON L25 (Source) and L30 (Sink), LED 16 will illuminate, but LEDS 4,10,22,and 28 will also slightly illuminate. Additionally, LEDs 13-18 will slightly illuminate."
  
  In using PLC on an LED matrix, you need to make sure your PLC source goes to ground when off and your PLC sink goes to Dcc when off (these are called pull-up and pull-down resistors).
  
  In this circuit design and if you only want one LED on at any given time, you can ONLY have one source and one sink on at any given time; otherwise, you will get multiple LEDs energized.
  
  L25 (ON), all LED's on L25 will have source.
  
  L30 (ON), all LED's on L30 will have sink.
  
  Only L16 will light.
  
  Now, turn on L31 also - LED's 16 and 22 will light.
  
  Now, turn on L24 also - LED's 15, 16, 21 &amp; 22 will light.
  
  You may want to use a multiplexer depending on your application.