heat sucks

Hey y'all I have an issue. My box is 32" high, 16" wide and 13" deep. Right now I have 3 14 actual watt 5000ks on 2 autos. There's is a fan, let's just say its pushing 50 cfm down low for intake and the same fan a little higher for exhaust. My temps are in the mid-high 80s...what do I do? I want to try either a passive intake, or a passive exhaust. I feel like logic says, I have too much heat, so I need to vent, but how big should the passive exhaust be? There is good pressure right now, and I did the lighter trick by the door, the intake, and the exhaust to make sure...help me please roll it up, you are my only hope.
P.S. bonus points to anyone who can point me to a lightproof breathable fabric to cover the front of the box with. Not a plastic type but something like a curtain material? Thanks so much in advance.

Cliffs:
Too hot
50 cfm active exhaust
50 cfm active intake
Do I do a passive intake or exhaust? How big?
Breatheable lightproof material?

So passive intakes are what you are saying. These should be below where my active intake is at the moment correct? I need the material for a myriad of reasons, not only light leak, which is why I need breathable as well. Thanks petflora, I have seen you give great advice to a bunch of newbs like myself. Oh before I forget...you say slots, but would round intakes with PVC pipe and 90 elbows to keep out light be okay?