Seedlings yellowish leaves and curling down edges Plz help!

[xuanlang]

Morning to the forum users! Need your kind help please..
I am not a beginner not an expert either, I have grown without any big problem for 5 years both indoor and outdoor with discrete results. This is the deal: I moved to another country and started my closet garden(first time using unknow seeds), now seedlings are about 18 days old and they got those following problems i have never met before:
-very light green color overall,
-yellowish leaves edges starting from older ones
-curling down leaves edges
-slow growth
After saying this , there are few of the seedlings doing quite well, growing at an average rate and not having yellow leaves, and they are in the same soil and got identical treatment as the other ones having problem!
Slow growth is surely caused by the low temperature, but leaves problem are not.

I tried give more light to one of them and got worse, tried Ph and it is about 6 to 7.
It is not a under-over watering problem.
they have almost no air circulation for now( though they are still small compared to the space available,and never met problems doing like this before).
Some seedling directly start with bad conditions, someone showed the sinthoms after a while, and couple of plants are growing quite well( all in the exactly same soil, same water, same light)
could just be bad quality seeds? Never happened before with brand seeds.

What Strain is it? unknow, bag seeds
How Many Plants? 15
Is it in Vegetative or Flowering Stage? seedling, veg
If in Vegetative Stage... How Long? 18 days
Indoor or Outdoor? indoor closet
Soil or Hydro? soil
If Soil... What is in your Mix? coco40% perlite20% universal potting mix 40%
If Soil... What Size Pot? 1 liter
Size (Wattage) of Light? How Many? 3 x 20 watt cfl 6500k
Is it Air Cooled? no
Temperature of Room/Cabinet? 14- 20 c° centigrades
PH of Medium or Reservoir? 6,5-6,8
Any Pests? no
How Often are you Watering? every 5-6 days
Type and Strength of Fertilizers used? not added fertilizer yet
Size or Square Footage of Room? 3 feet x 5 feet

Hope any Kind grower can give me some help, thank you in advance!

 

[Mono]

Your temps listed after the pics are rather low. Try and keep the grow room as close to 25 degrees C as possible. Do you know what your relative humidity is? Lower temps will mean it's higher!

Is there anything you can do to increase the ventilation in the grow area?

 

[xuanlang]

I also started thinking it's a humidity problem, humidity it's high, around 70% most of the day,I am not watering since a week or more and soil still moist.
I am thinking to buy a dehumidifier and a fan.
I tried fertilize a bit and seems no changes.. Ph is regular

 

[goathead]

I would do some reaserch on over watering and underwatering "google" or "bing' it for pictures or even check out the grow room links here. There was a thread I was reading about over and under watering and that seemed to have a lot of info. there is also the possiblity that there may be some root rot starting or allready established. seems like along time between watering. Are containers draining well?See any green growth near bottoms of containers or coming out of them? hard to say with out being there. keep searching, post what you find out please. Richie

 

[xuanlang]

I think you are right, I have never met root rot so I did't know of this problem... can I save my plants in someway ? thanks a lot!

 

[Mono]

Let the soil dry out completely. Go easy on the watering for a couple of weeks. They are young, should heal themselves over time.

 

[goathead]

they may grow a little slower until the plants decides if it is going to rebound. I believe I have couple that may be afflicted with the same problem they are approximetly 2 to 3 inches shorter than the others, germinated at same time, same love and attention given to all ladies. Some seeds have a fault in them I believe it is called natural selection or evolution. Only the strong survive! Mono is absolutely correct let soil dry and make sure it is able to drain! absolutely vital to help prevent mold. be careful it might kill the seedling by drying out the soil. I have tried to only use a few ounces of water on top and let bottom dry out. adding few ounces to top of dirt gives water to top roots and lets bottom air out. by few ounces I mean 1 or 2 least is better to kept her alive. maybe start with a half ounce of water then after few days whensoil is dry add another half ounce maybe three weeks to let bottom dry you will see change in plants if it continues to grow.