24 days from seed. no nutes added yet and using scotts premium potting soil. the soil npk is .7 - .1 - .3 the problem is also slowly starting to spread to another fan leaf not pictured..
You need to be alot more specific. What are your temp's? Could be heat stress. How close are the lights to the plants? Could be light burn. What size is that potter? Could be rootbound and need more space to grow.
Temps stay around 75-84, I'm using CFLs and there about 3 inches away. Pot size is half gallon and I've recently put in fresh soil and can say the roots still have plenty of room to grow in.
Marijuana Plant Abuse read it all the way through. it looks like you have a nute burn or P deficiency