Curling leaves. Suggestions appreciated

As I hope you can see from the pics the leaves are curling up a bit. This is my first grow so please be easy on me.

I am using a 400W MH light at about 2 ft distance 20/4 on time
Soil is a mixture of Home depot generic organic soil 40%
FF light warrior 40%
perlite 10%
worm castings 10%

plants are 2.5 weeks from seed, recently transplanted into 5G containers

Now with info out of the way I think the plants look good except for the curling. It happened about a day after I watered with nutes and I think it may be one of 2 things... the soil was not bone dry when I watered and may have overwatered?....or since I just transplanted the plants are using the nutes in the soil and I may have added to much nutes (Jacks classic orchid special 30-10-10, 50% strength) though I dont see signs of burn.

Comments welcome. A diagnosis would be great.
The only other thing worth noting is that during the lights out period the temp drops quite a bit from a constant 80F to about 68 within 1/2 hr of lights out.

+ rep for the voice of experience

Dito mine are doing the same

Can't be certain, so take this for what it is an opinion. I don't think it's over watering. From my previous experience with over watering they tend to curl in the other direction. Nute burn usually looks different too. I know you said your temp stayed around 80, but it really looks like heat stress to me. Do you know what the heat is right above the leaves? Not the ambient temps but the actual temps above the leaves. You might try running an 18/6 schedule too.

try lowering your temps or raising your lights.

Heat stress. I have seen it a couple times with my plant. She was growing so fast and getting to close to the light on warm days.

heat stress is my guess

yeah I agree I have seen a little bit on some of my plants recently. I think it's because of lack moisture and excessive heat. Try to bring the temp down and the humidity up I bet it will help.

do you see that the plant is praying for magnisum ??? try epsom salt next time you water 1 tsp per gl

heat/light stress ...check it out >>> http://www.ganjaguerrilla.net/Album4.htm

Thanks for the replies. Im gonna have to go with heat stress since that seems to be reoccurring. Humidity is 40% and that is the highest I can get it. The lights on temp is consistantly 79-80F. Its was under the MH at this height for a week before the problem but Im gonna raise the lights a bit more. My temp gage is right between the plant (can be seen in pic3) so I figured I was getting an accurate number. Ill post back in a couple days if it works for anyone watching this thread.

Triclone Friend I could not rep you before spreading around to others for some reason

seed2bud said:

Thanks for the replies. Im gonna have to go with heat stress since that seems to be reoccurring. Humidity is 40% and that is the highest I can get it. The lights on temp is consistantly 79-80F. Its was under the MH at this height for a week before the problem but Im gonna raise the lights a bit more. My temp gage is right between the plant (can be seen in pic3) so I figured I was getting an accurate number. Ill post back in a couple days if it works for anyone watching this thread.

Triclone Friend I could not rep you before spreading around to others for some reason

Click to expand...

Like i said mine are doin the same exact thing under my 600 hps.My room is 79 and the light is a good 2ft away.Im pretty sure its not heat stress or the light too close.Im leaning on it bein the magnesium problem.I hope im right cause im uppin the cal-mag next watering.