Well sayed arcadio.
Am still waiting for an answer for my poor seedlings needs!
not even a big plants.
Hope the guys above tell me what should I do for my stretchy seedlings as I believe that they are asking for more light appatently!!
Or am I wrong?
I have found that seedlings can take lots of light very early but they don't need it, they do well under 45W of cfl too. What I have done in the past is use a 600W metal halide for seedlings but I start with the light about 2.5 feet away just to be safe. Then every day I move it closer by about an inch or two until it is at a height of about 10 inches from the canopy (about as close as possible). Getting it this close with an open hood requires good environment control in order to keep temps at bay. You should definitely have a thermometer to know your canopy temp and just lower your light to the point that you are happy with while ensuring that the temps are ok.
But I don't know anything about your setup. If you are using CFL or fluoro lights then make sure they are very close to the seedlings, 3 inches max and preferably a bit closer. If you are using HID then stay on the safe side and keep the light a couple of feet away when they are newborn seedlings and gradually move closer (or further if that's your thing).
My gut feeling is that light isn't your issue. If it is though I guess you may either be using CFL too far away or HID too close.
Find out your relative humidity. Low humidity is very bad for seedlings. They like very high humidity ideally around 80% but anything above 50% will be pretty good.
What did you plant them in? If you used coco, that may be your answer. There are many cheap cocos that are very salty. I measured one that had a runoff of 1.4EC. This would be very bad if not fatal for any seedling. These cocos need to be thoroughly rinsed before using them. If you used soil it may also create a high EC due to containing strong fertilizers.
The other thing is your water. Most tap water is okay to use but there are some places with tap water that again has a very high EC (above 1.0) and will hinder or even kill seedlings.
If possible use R/O water. You can buy an R/O filter for under $100 that will produce thousands of litres of 0.01EC water which I've found is the best to use on seedlings until they are a few days old then you can slowly add your nutrients to ease them into their feeding schedule.
If you don't have an EC meter cheap EC meters work just fine. It is quite essential since it will answer many of these questions. Who knows whether it's the tap water or the medium if you can't measure it.
Finally if your pH is way off this will also be bad and depending on how far off your pH is will determine how badly it will affect your plants. If you are growing in coco/perlite or any other hydro setup you want pH to be 5.5 in veg and 5.8 in flower. If in soil then you want pH to remain around 6.3
Some cheap pH meters are okay but some are rubbish. It is definitely worth spending a bit more on a pH meter to get a descent one.