Hey BTK3ill
Bagseed won't show you sex until you put it in 12/12.
The droopy yellow leaf is quite normal. Those are cotelydons and they provide a source of nutrients for the plant until it has a viable root structure and enough true leaves to fend for itself. It's death signifies that the plant has exhausted the food it provided and that it's time for light refreshments. As it's still in veg stage you should use very low levels of growth nutes from now.
I think if you take the room temp and then the temp under the desk behind the case you will find that it's warmer under the desk. This is where the case is taking it's cold air from and this area will get warmer as the room temps rise, which they do daily until the end of the summer. That's why I suggested the tube from the intake fan to the side or front of the case where the cooler air is. If you can get some cooler air in there the plant will likely flatten back down. Otherwise another cup of water will probably do the trick. For now at least.
Reread this whole thread as I've covered the ventilation issues in some depth. It probably just went over your head at the time.