Seedling's first leaf set is curling upward along the edges. Cause?

Can someone identify what is causing the edges of this seedling's first leaf set to curl upwards?

Here are some specifications:

• Strain: Nirvana Short Rider (a short, feminized autoflowering strain)
• Age: 8 days since it first reached the soil surface.
• Humidity: 30-40% (might be a little too low, but I'm not sure).
• Height: about 2 inches.
• Medium: 50% Foxfarm Ocean Forest, 25% vermiculite, and 25% perlite. The seedling spent its first 7 days in a small styrofoam cup, and was then transplanted into a 3-gal bucket.
• Nutes: I have not used any form of nute feeding yet, and I do not plan to until I start seeing flowers.
• Watering pattern: this is difficult for me to define, but in a nutshell I've been watering whenever the soil surface gets dry. When I water, I keep watering until the pot starts to drain out water.
• Lighting: Refer to picture at the end of this post. I've placed two side-by-side CFL's that are each about 2 inches away from the plant. One of the lightbulbs is a 2700K bulb emitting 1600 lumens. The other is a 6500k bulb emitting 2800 lumens.
• Temperature: The ambient temperature is around 77-86 throughout the day. HOWEVER, it is possible that this temperature reading is misleading because the plant may be getting much more heat from being so close to the lightbulbs.
• The leaves don't seem to have any sort of discoloration. Refer to picture.

I didn't bother buying a pH meter because I assumed that this wouldn't be a problem since FFOF seemed trustworthy enough to keep my pH in a comfortable range.

I've been searching around the internet for possible causes, but I haven't reached a definite consensus. So far the possible candidates that are causing the curling are:

• Overwatering
• Underwatering
• Too much heat
• Too much light?
• Too low humidity

So which one do you guys think it is? This is my first grow, so I'm a little confused. It could be possible that the slight curling isn't a problem at all. Please give me your thoughts. Thanks!



Pictures:

Picture showing light set-up:





Aerial view of plant showing leaf curl:

They are the seedlings first leaves , soon if you dont pull them off , they will drop off , nothing to worry about imo

So I'm supposed to disregard the curling?

i do yes , there is nothing that needs to be done, i will post a picture of 1 of mine gimme a sec...

Blue mystic seedling , same age.

Its heat btw... as in, too much.

Your one looks fine but Borealis one looks burned , maybe the lights are too close and too hot and burning the leaves .

Yo the ffof is still to hot for yo seedlings!
Even if you cut it with whatever~
If it keeps gitting worse yo know~

Alborosie said:

Your one looks fine but Borealis one looks burned , maybe the lights are too close and too hot and burning the leaves .

Click to expand...

Look closer at my tips the ends are curled , its not heat , his new leaves are fine , it happens on every seedling , the first set of leaves on a seedling are like an umbilical cord , it does not need them after a while.

Your plants look a little like mine did. Mine suffered the most with the next set of leaves after the single set. If it's the same thing I was experiencing, then it's a combination of several factors.

Your soil is too hot for seedlings.

Your temps are getting too high at times. If you are seeing 86 degree room temps then the plants are getting even hotter since they are right beside the bulbs.

Your humidity is probably a little low, especially for seedlings.

That's just a guess though, based on my own current crop and it's similar appearance to yours. Get on top of it or you will continue to see these symptoms. That next leaf set will start doing the same thing after it matures a little more. Mine were on the fourth node before they really straightened up, and now I'm prematurely losing some of those lower fan leaves that were damaged.