I have no idea what's wrong with my plants.

It's my first grow, and things have been going pretty well. I give them nutrients every other watering, and they are growing pretty fast, also giving them some co2 from my co2 tank, i'm not sure if that is what is doing it to him, because it's really only on this plant. I'm not sure what is wrong with him. I've never read about this deficiency.

Don't call her a him she doesn't like that very much Unless it really is a him lol
Have you been foliar feeding? Some of your nutrients may have gotten on the leaves and burned them.
The leaves can also grow abnormally if they are not getting enough exposure to light. What type of light and nutrients do you use?

I use a fox farm blend, I do the regular amount is says to use, so i don't think it has anything to do with that. I had been spraying the room with some water it might have gotten on the leaves a little, but I didn't think that would make a huge difference, would it? And It's a her, sorry. I was typing fast haha. Also I have a 500watt fluorescent light which I can crank up to 750 or 1000 if you think that will help.

Well if only the lower leaves on the plant are effected I would say add more light, but your last pic looks like the top of the plant.
It could also be a heat stress issue, plants sweat just like animals in hot conditions and if the leaves are too close together without enough airflow. Do you have any ventilation?

yes, I have a circulating fan, also a van blowing in air from outside the room, and a small area that lets out the hot rising air through the attic, I'm starting to think it might be a light burn or a nutrient burn, judging by the pictures i've seen on other sites and google.

Nutrient burn is usually first spotted when the tips turn yellow or brown and the leaves will be dry and crispy to the touch. I don't see any burned tips in your pictures and it looks grean & healthy for the most part, are you sure you didn't splash some nutrients on the leaves accidently while you were feeding? It's a common mistake I still make it sometimes

It would be the slightest possibility, but it is indeed possible, but if i did, could that be the cause of it, because it's really only on that guy, and my leaves feel a little dry, but then again, it is my first grow and i'm not sure how they should "feel" exactly.

It might be a potassium or magnesium deficiency, but most likely a deficiency not nute burn. It's really hard to tell from the pics maybe another grower can chime in.