My plants at 12 days and new grow box

I finally build me a CFL grow box and my plants are 12 days old and finally starting to grow a little, I did notice a little something on the tip of a leaf it looked kinda dried up but it was just the very tip of 1 leaf.
http://i526.photobucket.com/albums/cc343/c4rb1ne420/cab1.jpg
http://i526.photobucket.com/albums/cc343/c4rb1ne420/cab2.jpg
http://i526.photobucket.com/albums/cc343/c4rb1ne420/pb-1.jpg
http://i526.photobucket.com/albums/cc343/c4rb1ne420/pa-1.jpg
I;m not great with a camera sorry, but the 1st plant has had a yellowish color ever sence sprout and the 2nd is the one with the little brown tip on the right (hard to see).
I orderes a 4" inline fan and a filter from HTGsupply 5 days ago but it still hasn't been sent out. The box is almost airtight and seems to be cutting down most of the air my temperary fan can push through the hole, should I make a little air hole for fresh air?

Anyone have any opinions or see i'm doing anything wrong please lemme know

looks good, you def want an intake of some kind, either a hole or another fan.

right now im useing a crappy little 4" desk fan from walmart for the exhaust, whenever my 4"inline fan comes in I was thinking about drilling 3or4 1" holes together near the bottom and putting the crap fan there blowing in.