are you running them on a computer power supply, or on a power block like a cell phone uses? if you are running them on a cell phone power block or something similar, what voltage and amperage does it say for Power Output? if you already know about this thats cool. but a lot of first timers dont know that fans are rated on a certain voltage and watts. they will work on less voltage and watts, but they will be slower. They will also work on more power, dont know how much may be too much, but their life will be shortened by this.
a bunch of growers i follow on here, and myself, all tried removing any circulation fans and/or intake fans to improve performance. it helped every single one of us. i think what was happening is these fans were mixing the hot air up and not giving the exhaust a chance to remove it, causing the cab heat to build. sorry it didnt help you, but it may give you some thoughts to work with.