So what I can guess is what happened to me for the first few weeks.
You need to use fresh soil, mix your nutes extreamly lightly. If you need to, boil water for 10 mins, let it cool to room temp and then use. If you have some hydrogen peroxide, mix about 1-2 ounces to 1 gal water and always shake your container up well and secure it in a dark place when not in use.
Some might disagree with what each of us have to say but this is a safe bet to not start over.
Hydrogen Peroxide at the household level is very low percentage and is a wonderful bacteria killer. It also provides oxygen on breakdown.
I have used it in every gallon I have poured.
Your lights could be too close. People here are saying to put them 1-2 inchs away... I don't think so. It hasn't worked for me at all like that. Also do not put your fan directly on your plants. Best would be to aim it up at the lamps so you get them to cool off a bit and you get a flow of air going around the plants.
You don't need a CO2 tank, just grow them in your room with the closet door open at night. Humans produce mass quantitys of CO2.
432L of CO2/day That would be 36L/hr. I think that should be enough to improve plant life don't you..?..
After my improvments this is my result on day Veg 24