IF your light is air-coolable, I would swap out your fans so that big one is on the light. Also consider insulating the duct from the light to the fan.
Remove all obstructions from the passive intake and make it twice as big as the total exhaust hole size, including the exhaust from your light.
Make sure the exhaust from the light is not going into the space that the intake is pulling from. Send it into a different room.
A/C the room where your intake is coming from.