HELP .. my beans can't live on the SUN!

[Cesar Chavez]

Ok.., here I grow:
GrowLab 80L (2’7”x4’11”x6’7”)
Sunleaves Pioneer VIII (Eight HO T5 Grow Tubes 6500K)(47x25.5x2.75)
EcoPlus Inline Fan Classic - 4” (160 CFM)
Can-Filter 9000 - 25” Carbon Filter
ThermoFlo Insulated Ducting - 4”x25’
Honeywell Thermo-Hygrometer (Placed half-way up an inside wall; wireless sensor)
Honeywell Tabletop Air Circulator (x3) No oscillating fan.

So my problem lies with 'temperature control'; I live in the desert. During my day cycle, 4pm-10am, my air temperature rises to as much as 82, before steadying out at around 80. During the night cycle, my temperature goes as low as 72. I would like to ideally go no higher then 77-78ish, and drop no lower then 70. I am seeking feedback to help drop my temperatures. Should I rearrange fans in order to maximize cooling? Buy another inline fan to bring cooler air in from bottom? I am only using 4 bulbs at the moment because all 8 are pushing out alot more heat; but if I could find a way to cool them, I would rather use them all. I thought about placing the fans underneath the cedar bench facing directly up, think that would help push the heat up more? Any and all information, and/or suggestions, is appreciated. Thanks.

*I have my wall a/c unit set on 69.
**Thermo ducting expels air into another room.
***All bedroom doors are closed.

Ps
I fried nearly 90% of my beans in the beginning because temperatures were way worse. Through research and this forum, I was able to get it down to my current stats, but just cant seem to get it down a little more. Please help me so my beans don't try to survive on the surface of the sun . Thanks.

 

[Cesar Chavez]

A few more pictures to give you the full lay out. Thanks.

 

[Cesar Chavez]

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[pcduck]

Just by a quick glance I would say that if you got a bigger fan(300+cfm) and had your lights on at night might help with the heat. Most growers try to refresh their room 3-5 times a minute.