A larger fan is going to need a larger filter, and that filter you have is the bottleneck already, along with putting a 90 degree bend right at the exhaust.
At the very least, try moving the fan to a straight run of ducting. That will reduce turbulence, increase pressure, but that filter is seriously small for that tent.
Can you return the second fan and get a larger filter? I just can't see how to squeeze that much heat thru such a small filter. Even if you do, the smell will pass unless you filter slower