Let's see here... chances are you are doing a combination of things. If your soil has any nutrients in it, your plants run a higher risk of having problems when they are that young. Since you mixed it 1:1 with neutral soil, it could have "cooled" it off... but applying another fertilizer just brings you back to the hot soil. By the looks of it... where your plants are at now is probably when you wanted to start introducing a weak nutrient solution (4-5 nodes or sets of branches) IF you had started off with a relatively neutral soil mix. Seedlings can thrive with just pH adjusted water and light. Also, since you have been applying fertilizer... what is the NPK of it?

About your medium: While it isn't really bad to have a chunky soil composition... that much bark will make it difficult for roots to stretch quickly, as they will have to make a detour around the hard chunks. Perlite is the probably the most commonly used material when trying to increase drainage. Also, what kind of bark is it? I'm guessing you just got it from the woods?
You also want to fill the pots to about 1-2 inches below the rim of the container. You want nice airflow over the soil surface. That much space will create stagnant air which isn't optimal for indoor growing and can promote mold/rot/funkyjunk. You can fill the container up more, as long as you don't bury it deeper than the Cotyledons (first set of leaves). The main stem will grow roots anywhere below that set of leaves.

Oh, and you want to make sure you don't over apply your fertilizer when your plant is ready for it. Your plant, most likely, will not want food everyday. Cannabis likes somewhat of a wet/dry cycle. Meaning it likes to have the roots fully saturated... and then left to suck up all that goodness. Once the majority of the moisture has left the soil (the pots will be considerably lighter) you know that your plants "cleaned their plate." Now it is time to feed/water again. Sometimes it can be as long as 4-7 days between feeding/watering. Also, you want to be sure to flush the soil of salt/fertilizer build up that can create pH problems and lockout conditions. Actually, maybe once your soil is dry enough to water again... you'll want to do a thorough flush to clean the soil a bit? Knowing the pH of EVERYTHING you put into the plant is crucial. The best nutrients in the world won't do a damn thing if the roots can take them in. pH adjustments in soil are usually made to roughly 6.9... but it depends on your situation and what you are trying to accomplish.

I don't know about your light, so you're on your own for now :jointsmile:

Oh, and you need an active ventilation system. Just opening the door isn't going to be enough. Some type of constant air exchange is going to promote healthy growth. You will run the risk of things like mold, rot... and heat stress can result in less yield, hermaphrodites, and probably other things I don't know about.

And lastly, don't be freaked out if the plants don't all behave the same... even if they are all the same strain. While they may have the same "name," they are not robots and behave just like any other living thing. All humans start out the same way... but we don't grow at the same rates and get sick for different reasons. And just like the plants.... WE WILL DIE IN THE END! Muhuhuhhahahahaha :stoned:

Hope that helped :rasta:

P.S. Read Stinky's guide here:
http://boards.cannabis.com/basic-gro...-dankness.html
I need to make sure that I explain: THIS IS MY BIBLE :hippy: I wouldn't be able to pass along info had it not been for my almost daily reading of this thread.