I think I might be able to offer some assistance or ideas if your ok with that.
Why not use the whole room you put your grow box in? The tighter the space, the more issues it seems to me? It works OK but can slow your learning curve because it opens up the potential for more problems IMO. I have used 4x4 and 4x8 tents. Air flow is critical as you can get hot zones and, with the tents have to consider outgassing.
Why CFL's?
I started with CFL's also. I had five 36" bars that had six sockets each with a double adapter on each. They work fine but do not give the best results IMO. Because of their shape they don't distribute the light as evenly as a regular Floro allowing you to get an even lower canopy. Lot's of waisted light and by the time you add enough of them, you could have bought a nice HID in cost and electric. No matter if it's a 250W, 400W, or 600W, my plants explode when I move them under a HID. My preference is a 600W and I also use 1000W. The difference between a 400 and a 600 is HUGE and my cloning phase, with floro's takes them past the value of a 400W for me. Adding more 400's lights does not equal the depth penetration of a larger W ballast. I look at 400's like CFL's. Sure, everybody uses them and they work great.
Stick to proven methods. No shortcuts or reinventing what works until you know what your doing so you know the difference.
I have never NOT used RO water. IMO that was your first problem. I soak my RW in 100ppm nutes for my cuttings. Then it's a week before I need to consider watering them again. If your supposed to give your plants 100 - 150 ppm of usable nutes but you've already given them 199ppm of ? iron, chlorine, etc... See what I'm saying?
Mist them every few days with a couple ML's of grow nutes per quart.
ALWAYS check and re-check your PH and PPM. Meters are a MUST! Sure, people say... But it's just a guess. Once you have it figured out you won't need them as often, I guess. I keep one in each rez giving me readings 24/7. They are worth the money and my most valued tool. Spare no expense.
Bubblers are tuff. I've done dirt, ebb&flo and various forms of areo and have yet to come close to the growth rate of any listed with a bubbler. It seems to me that the RW has to stay, almost dry in a bubbler even after roots drop. When well rooted a soaked RW cube is no longer an issue. Loose the drip line and use a squirter to water the cube when needed. Just a ML or two will keep you golden, not soaked, just moist. The more bubbles, the more roots. Once the roots start to poke through the rocks, lower your water 2" below net pot and let the bubbles cracking at the top of the water act as a areo. Change the rez once a week if you want. Seems to me I get a boost of growth at each rez change.
Forget about all the extras and stick with a good A&B nutrient. No Superthrive or whodoo voodoo. Just the basics until you see what it takes to grow properly then you can expieriment.
I think your second problem after RO is/was heat from your lamps. In one pic I see you had a tent of lights surrounding your seedlings. Room temp maybe 80 but the radiant heat from those CFL's is the main culprit IMO and drowning them. I would advise to raise the lights up.
CHILI POWDER. Forget about it. Get some ant spray and spray around the outside of the grow box. Terro will wipe out the whole ant community. Get a fly strip now also, just so you'll know what's there. Mice ate 100$ worth of AK-47 seeds of mine in a basement grow.
I wouldn't top that plant yet! It's not even a plant yet. It's struggling and suffering enough as is. Why would you want to stress it out more?
This is a good point in hand. Use some discretion in following advice. Sure everybody says top at 3 or 4 full leaves, like yours, but yours is NOT healthy and THRIVING. Same as giving 3 week nutes to a three week old plant that is more like a 1 week old plant from the guy giving advice.
I run big plants and I top them when they are ready. Not when I'm ready or by their AGE. On topping young plants you want to wait until they are healthy and growing rapidly. I wait until secondary branching is WELL established so there is not really a lag in growth after taking the tops. I also raise my floros up more than most to get a little stretching. I know the shortest, most nodes per inch is cool, but all that cool is just going to get chopped off as they get bigger. I try to keep the thick stalk while getting a inch or two separation in between the nodes.
ENVIRONMENT is EVERYTHING! Not nute loads.
Example. I'm at 3 weeks of 12/12. My plants are 5' tall with several main colas each. HEALTHY and thriving with no burned tips. My nute schedule following AN's "Light feeding schedule" with a 15 gal rez calls for;
3.5 oz A
3.5 oz B
2.17 oz MET
2.17 oz H2
2.17 oz F1
6.53 oz B-52
2.00 oz Carbo
11.0 oz Sensi
.75 oz Piranah
.75 oz Tarantula
6.80 oz BB
I just changed my 15 gal rez with;
3oz ea A&B
6ML BB
1oz Carbo
4ML of all the rest above.
I do not use Sensi, Piranha or Tarantula.
I will continue to raise the doses until they don't want it and I can tell this by their leaves curling, folding, color, turned down, etc... I can see these things before I get brown tips. I also judge this by their water to nute consumption from reading the PPM meter.
I write that just to show how little of the recommended nute load I am using. My first year of growing I tried to half the nutes recommended and everything was trash.
Stick with base nutes and add extras as you choose in very small doses and examine results before adding more or others.
I hope I haven't come across as a know it all as I'm still green myself. Not trying to talk down, just read your thread and thought, hey, I did that at first also. Hope you can glean something use full from it.
Don't sweat these mistakes and problems. I look back on my beginning efforts with GREAT fondness. You can only loose your virginity once! When you get it figured out, these trials will mean the world to you. I wish I could do it again. Have fun with it.