I would suggest that the wiring is much more involved more than you are aware of. When Paralleling Linear (assumed) regulators the one with the highest voltage will supply the brunt of the load... until it's voltage drops slightly due to load and then the next closest regulator (in output voltage as they are Never exactly the same voltage) woll take up what it can supply until all are sharing current according to the separate voltages of each regulator. In this respect Linear and Switchers are the same and NOT the same as batteries. Unless it is a very special type of linear or switcher it cannot sink current so there is no interaction where one is trying to "charge" the other to it's output voltage as a linear or switcher can only source current it cannot sink current... unlike batteries which Can cause major damage if of unlike terminal (output) voltage. Paralleling regulators isn't the greatest of ideas AT ALL (better to split the source voltages and keep the grounds all returning to ONE common point) by using a star ground layout and separate sources. The reason is that there is no way of insuring that all are created "Equal" and if one fails or is really low in current capacity it will be masked by the "Better" regulator and you might well find "Weird" behavior. There is also there is the thought that the higher "input" voltages will suffer proportionally less "I-R" drop than trying to supply each board from a common supply.
Bob