I haven't done a hourly monitor. It's been more haphazard, at best. I think both of you, stinkyattic and TheMetal1 have hit the nail on the head.

The intake is passive and limited to the 3 flaps at the bottom of the tent plus a 4 inch duct coming in at the bottom. It did better last night with the bottom zippers open and allowing more air in.

I'm thinking of redoing my exhaust, as well. Right now I have a DIY carbon filter running into 6 inch flex duct and then to an 8 inch 500CFM duct fan. I have the fan mounted outside (on top) of the tent. My thought is to eliminate the flex duct and just connect the filter directly to the fan since each bend in the flex duct cuts down the CFM.

TM1 ~ Here's the pic you requested. The fixture will actually hold up to 22 CFL's. When we go to flower mode, I'll be running all 22 but with 2700k bulbs instead of the 6500k ones in there now.