Strange issue w leaves?!?!?!

Hi All,

Hoping someone can offer some thoughts on what the issue may be with the yellowing of the first true leaves on my 3 week old seedling.
The Cotyledon laves have just yellowed up shrivelled and died, which is all well and good, but no sooner had this happened, the first true leaves began yellowing, and now looks like they could fall of too.

If this is just because they are not needed, like the cotyledon then thats fine, but i wasnt aware, and havnt read this or heard of it before...

Anyone able to clear this one up or offer some advice at all?

They are still under 6500k CFLs, which are about 6 inches away form the plant.

Water is treated tap water, soil is at this stage, just standard potting mix, thought it could have been a possible Nitrogen deficiency, so gave the plant its first weakened nutrient solution (thought it was almost about that time anyway)

growth is also appearing stunted, my other healthy plant has taken over in size over the past few days, im sure that could mean something too.

As always, any advice would be greatly appreciated, books are great to learn, but they just don't have the practical advice when this type of shit happens, you have to make the mistakes i guess!

Few pics below also.

Thanks

get the lights within 2-3 inches. does that container have holes in the bottom? how often are you watering? how are you deciding when to water? have you been checking your waters ph? do you have a fan blowing on it?

Thanks for the reply; moved the lights...

The containers are seedling trays, and they have large holes in the bottom, I am watering about twice a day at this stage. I am using a misting bottle/sprayer so they tend to dry out quite quickly. I am checking them often, and i water when they top of the soil looks dried out, I have started upping the amount of water as they are mostly 3 weeks old now, i watered thoroughly until water came form the holes in the bottom for the first time at the weekend, but this didn't help either, so back to a thorough spraying a couple of times a day, they don't look big enough to need anything more at present. I have a fan i the cupboard blowing on them constantly, and i dont have anyway to check the P.H of my water, apart from sticking my soil ph moniter in there which i just did and it is about 6.7....Not sure if this helps, or is accurate.

Can overwatering produce a yellowing of the leaves like this?

P.S i havnt installed the ventilation in my cupboard yet so when the door is closed they are not getting any fresh air, but i am leaving the door slightly ajar for them to get air, i am in Sydney (Aus) and the weather is hot and tends to not be too humid either, i have a tshirt soaked in water in a bowl, that i re-wet every few days to try and keep the humidity at a decent level...

Looks like its having some heat stress, do you know the temp? Yellowing is caused by a many reasons, but it looks like the plant is drawing the nutrients from the bottom leaves to produce new growth. so start feeding at 1/4th strength.

I have a thermometer, hydrometer thing in the post, should be here tomorrow actually so ill know then.

The healthy looking plant pictured below is a Utopia Haze, and seems to be doing okay with the heat, but brazilian genetics, so im guessing it can cope a lot better with higher heat, the struggling one is a bagseed, so could be anything, but interesting that i have another bagseed, pictured second, that stopped growing about 2 weeks ago, just out and out didnt move up anymore?
I also have another utopian Haze plant, not worth a pic, that sprouted, grew two true leaves, and then didnt grow another Millimetre after, and is still alive but just has never grown at all.
Possibly could all be related, but not sure at all. I would love to get it straightened out before anything happens to my healthiest haze plant!

First is the haze, second the bagseed

the medium your growing in looks too acidic,which causes nitrogen lockout.

your watering all wrong my friend and have been, thats why its so small and not doing well. When you water give it a thorough watering everytime. you want the soil thoroughly moist, run off is normal and is good as it helps leech out salts, i use about as much water as the plants container size each watering. ( 1 gallon pot=1 gallon of water, 3 gallon=3 gallons, etc). let the soil get light again before watering again. here is a link that will explain it a bit more-
http://www.uk420.com/boards/index.php?app=tutorials&article=233