You must have been playing on different sized maps - game speed as no impact on corporation output. Think about it. All the tiles generate the same amount of food/commerce/production at any game speed. It's everything else that's changed to fit round it - production and research costs are mostly three times higher.
Similarly, that already compensates for corporation output. If you cut corporation resources like that on marathon, they'd be three times weaker than on normal, since production costs already take into account the change in game speed. Fortunately the does not work as you suggest here, and game speed has no effect on corporation output.