I'm no expert but a 6" fan/filter sounds like way to much cfm for a 2x2 tent. I have a 4x4x7 and the 6" inline fan was imploding my tent like a black hole, even with the bottom vents open and the controller set to low. Loud too. Now I'm using a 4" inline fan/filter on medium speed with two 4" booster fans for intake (instead of the mesh vents to avoid light leaks) and it still pulls the walls of the tent in a little for negative pressure. I'm pretty sure the air exchange rate to shoot for is once every five minutes. So for my tent that has 112 cubic feet(4x4x7=112) the 190cfm 4" fan completely circulates the air about once a minute on medium speed with a carbon filter. Your 2x2x4 is only 16 cubic feet...you're gonna be movin' some serious air through there man. Humidity might fall off hard. I think I read somewhere that 4" inline is as small as you can go to still use a carbon filter though. Who knows though, that 6" might work great. Trial and error kind of stuff when you first start out.
As for smell advice, the carbon filter was simply not enough so I got some Ona Pro. I put a small dish of it right in the ducting just past my furnace and it treats the whole house. It dries out after about a week but a gallon should last a whole cycle or more.
Plant looks ok to me, maybe a little bright on top, but I'm a hydro guy so I really can't say for soil.
Looks like it wants to be a tree, nice job.