Leaves are turning brown and curling, pics included

Around 2-3 weeks ago a buddy of mine was trying to get rid of 3 baby MJ plants and being a MJ lover I just couldn't let them be thrown out. Well I very short notice I managed to make a 4 X 4 X 4 plywood box, which I question if that was my first mistake. I got some full spectrum florescent bulbs, low wattage(under 50) and I think that was my second mistake for not getting a 400w HPS light. I bought excellent soil that meets the standards, or what most people say are the standards, on this forum. I have a pH checker and the pH is always between 7-6.5 and I water only when they absolutely need it. Just in case I have a moisture reader too. I also have a small fan set up. I bought Jacks 20-20-20 and Jacks Blossom Booster. Now one problem is, when I recieved the plants I immediatly transfered them from some terrible soil into the new soil, and I read that you should not fert your plants until they are 3 weeks of age due to there being plenty of nutes in the soil. Well my plants were older then 3 weeks when I got them and I moved them into the new soil and I don't know if I need to wait 3 weeks after moving them or if I can start the ferting them. But another mistake, before I found out I leaf fed them, only a couple of squirts a piece. I added half of what it said on the fert container, like I have read over and over. But what worries me the most is the box I made is for a stealth grow, and I don't have any place for the air to flow out because the holes that are on the top of the box are covered in blankets and it gets very humid in the box and I recently found white mold growing on the top of the soil, which I personally think is the problem here but I want to be sure before I try anything else. So with what I have told everyone I would greatly appreciate it if somebody would tell me what they think the problem is.

So someone please help!! And here are the pictures.

I have a moisture tester and i water when its dry and when i water i do it evenly through the pot untill water comes through the bottom

That's a lil to much water u should only put about 2-3 cups of water but I'm new to growing and that's helped me out.

It sounds to me like your plant went into transplant shock and because of it's inability to use the nutes, suffered from nute burn. No more feeding for at least a week. Continue with normal watering, but they may die. If things don't look good in a few days, last resort is a soil flush. It's also not helping the plants that you have an inadequate grow room. Get some ducting, drill some holes and buy an inline fan for some proper airflow. You may just want to abort this whole mess until you have a proper grow room.

I just got a couple of computer fans and i am in the process of drilling holes and im going to have them pulling the air out.. Will this fix the problem?

And i transplanted the plants almost 2-3 weeks ago and growth never stopped, this started happening around a week ago

Danijuana said:

I just got a couple of computer fans and i am in the process of drilling holes and im going to have them pulling the air out.. Will this fix the problem?

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I'm not sure how much a PC fan will help (how many CFM?) but it is definitely a step in the right direction to getting your grow room to cool. Don't forget to include a hole for intake and use a screen to prevent dust.

Danijuana said:

And i transplanted the plants almost 2-3 weeks ago and growth never stopped, this started happening around a week ago

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I still think it sounds and looks like nute burn since this occurred after you fed them. Did you use 1/4 of the recommended dosage for the first feeding? I would lay off the nutes until your plant is looking healthier. Don't over water them either.

They look really spindly and leggy for a 400w. How close are they to the light?

What Midnight Joker said. Also, that dirt looks really dark. What is it? Doesn't look like it has much perlite in it. Should have about 30% for good drainage. If you have good drainage you can flush when you need to with fewer worries about over-watering. If that dirt is as rich as it looks, it probably could get you through at least til flowering without adding nutrients. Here's a pic of my veg tent, the dirt is showing in the container in the back left and you can see how much perlite is in it compared to yours.

When i mixed the fert i added 1/2 the recommended because thats what i read.. And the soil contains plenty of pearlite.. The water drains through quick and it also has the substance that starts with a V that holds water, along with worm castings. And they look spindly because i dont have a 400 watt bulb

After a transplant, you want to wait 3 weeks to feed, then feed at 1/4 strength. You can then slowly increase your feeding schedule.....

Got any new pics of the plants to see how they are holding up?

just from looking at the dirt i think u need more perlite........IMO..........if those were mine id flush them when i could (soil looks real dark not sure if its wet) .once the soil is ready to flush do that then i'd cut off all that black or messed up leaf ....mix up some neem oil and spray that on once a day ....you have no real heat with your lights so lower them to about 3-4 inches above plants

Also, when I check my soils moisture the top to middle reads dry but when i stick the tester all the way in the soil, it reads the highest moisture level in the bottom but this is 4 days after the last watering.. Do i water them when it reads like that or do i wait for the entire pot to be dry?

Danijuana said:

Also, when I check my soils moisture the top to middle reads dry but when i stick the tester all the way in the soil, it reads the highest moisture level in the bottom but this is 4 days after the last watering.. Do i water them when it reads like that or do i wait for the entire pot to be dry?

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wait a while u want the roots to stretch and grow to reach for the water

Get rid of the blankets as they need circulation of fresh air.
Let the soil get really dry and crusty before watering again and no nutes for awhile.
Next, get some lights on those babies to fill them out.
Check out the various threads on cfls as a cheaper way to help your grow.
Keep us updated. They can go 12/12 soon, I think.