please help! seedlings turning pale.

Hi, this is quite a long one so please bare with me.
I've been growing for about seven years now mostly outdoors, but i have grown indoors a few times as well.
I'm growing eight different strains(20 plants) from seeds which I've bought from a reputable European seed company.
Grown under a 400 watt mh,
The temp at plant level is stable between 70 and 80. RH stable at 60. ph of soil 7. (I've been using this organic soil for years and never had a problem) ph of water 7. (tap water standing over night same as I've always done.)
The room is 10 feet by 12 feet with two 6 inch passive air intake holes.(the door opposite the intake holes opens and closes a few times a day. the pots are about 6 inches tall and 5 inches wide. The first three weeks i watered every other day sometimes every day.IN the first week after germination i had them about 30 inches away from the light and after a week I got them to 23 inches
The problem started showing at about week 2. the true leaves were becoming a very light green and started to yellow from the bottom. growth slowed down as well. at the beginning of week 3, I started watering less, every 3 to 4 days, because I noticed that I was over watering. today is the start of week 4 and i am yet to see improvement. more bottom leaves are yellowing and even new leaves look pale ind sickly. i have moved the lights back to 27 inches. I know 18 inches is ideal, but they are still young so i just want to make sure its not too much light. I also gave them quarter strength organic nutrients at start of week three.(just to be sure) I didn't feel the need for my 6 inch exhaustt fan yet as i wanted a little more humidity for the young seedlings. I have had a oscillating fan gently blowing over them since day one. how long before you see recovery from over watering?
Should they not still be nice and green even when over watered? I switched my exhaust fan on today as well. All of the plants are affected however some looks to be more resistant than others. I still have them under the one light, but when i flower i will have 8 plants under two 400 watt hps and the rest will go into my greenhouse. No sign of neut burn. just lime color leaves yellowing from the bottom. also i doubt its deficiency because I've grown in this soil start to finish without adding any nutrient and they've always been a nice healthy green.

we need pictures of plants and soil

Sounds like a Nitrogen Problem ,but pics would help.

LOL--Grower13, IU seem to be following you around and echoing your posts. We do need specific information about soil and nutrients and pictures of your plants. Just saying organic soil and organic nutrients doesn't tell us much. Who exactly did you get the seeds from and what strains are they? It can be hard to grow that many different strains as different strains can and often do have quite different nutrients/watering needs. One reason that we often encourage new growers to go with 1 strains and learn it is because different strains do have different nutrient needs and like different environments sometimes. Do not expect all strains to act the same to the same environment and feeding schedule--it just doesn't wok that way.

How long it takes to recover from overwatering depends on how good the drainage capabilities of the soil are. If you have a soil that does not drain well, but holds water, it can take a long time. If this condition exists, your soil may need attention.

Outdoor and indoor are way different animals. IMO, you need ventilation all the time--i.e. the exhaust fan should be running all the time. If you do not have good air exchange, the plants are using the same air, which becomes depleted of CO2 very quickly--a matter of minutes sometimes. Plants need a continual supply of fresh air all the time the lights are on for proper photosynthesis.

Do you have some kind of reflective partitions up? A 400W MH is only good for about 10-12 sq ft max. If the light is simply put into a large room, like a you hae it now, the light is disbursing throughout the entire space and you are loosing most of your light. In other words, the plants are not receiving enough light.

OK while I'm figuring out to post my pictures I just wanted to ad that the reason why I dint care to name the soil I'm using is because I'm from South Africa and you guys would probably not recognize the brand, but Ill give it anyway.
It reads organic potting soil manufactured by C.S.M organics.
The nutrients I used was from a dutch company biobizz bio grow at quarter strength, 3 to four times over a 2 week period.
Seeds are from The attitude seed company. I bought 3 holy grail kush, 3
white widow, 10 the church and then I got andromina, fuego, pure kush, power kush and truthband as freebies. All of them are affected some more than others.
looks like a nitrogen deficiency except newer leaves are also a lime color.They dont look like they're dying just sickly.
I see what your saying about the light. I can provide as much light as the plants need, but what Id like to know is at this point should i give more or less light. I have vegetated under these lights many times without a problem. I normally flower in my greenhouse.
Things I've done differently this time is I've went and gotten all the gadgets. pH humidity and that sort of thing and I've actually improved the ventilation a little from last year. I've never even needed an extractor fan and only bought it because I'm planning to flower indoors this year as well.
The biggest thing i did differently was the seeds, I've always used local, sativa bag seed.
High grades are very rare where I live and anything with a thc content of 15% or up is almost unheard of.
I ll be posting those pics soon!!!!

Usually we can find some kind of information on the soil, even if the person is from another continent--the web is world wide. However, I was unable to find anything about your soil. I asked because not all organic soil is created equal. Can you tell us what is in it?

Have you used anything in your soil that is not organic? Using any kind of synthetic fertilizers or additives can kill the good micro herds in the soil.

The biggest difference is the seeds. You have gone from lower quality native seeds to high quality genetics. It can be a whole new ballgame. Do not expect all stains to grow like one another, especially going from some kind of landrace sativa to mostly indicas.

Here are a few pics of a previous grow under the same light same soil and same room. I want to see if I've gotten the posting right. Then I'll post the problem plants.

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Ok finally here they are. I could not find any more info on the soil. And I did not put anything else in the soil other than what I already stated. They might not look as pale on the pics than what they do in real life. I've put one of my sativas which I've been growing outside in the greenhouse next to my strongest looking high grade it is pic 6 I think, and you can see the difference.
Please tell me what you think and thanks for all the help so far.

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O and I've added 30% perlite

They look hungry to me. They need some Nitrogen for starters I think. Do you water well then let dry? that is a good way to do it. They are quite stretched but if you repot them you can bury the stem.

Nitrogen and dont over water.

They look hungry and they are stretching--more food and more light.

Ok will do thanks