One week old sprouts keep dying.

I ordered some northern lights seeds, and a few other strains. I have the capacity to grow two plants at a time, so I started with two northern lights seeds. I started the seeds off in 80% perlite and 20% coco coir. I didn't have the containers covered, and I kept a 42 watt CFL about 6 inches above these. The seeds sprouted and came up quickly, but after about a week the stem in the middle looked liked it started to wear out, then the sprouts limped over, eventually dying. 
 
Someone in another forum told me that I had my lights too close, and because I didn't have them covered they might have dried out. I tried something else then. this time, using the same growing medium, I kept the containers covered with a plastic cup, with some air holes, and I kept the same CFL about 12 inches above the container. My sprouts came up again quickly with little problem, and looked like they were doing good, then after about a week again these sprouts too limped over, and again it looked like the stem started to thin or rot out in the middle. On another forum a grower told me that my sprouts probably stretched too much because of the distance of the light. 
 
I tried two more seeds again after this, using the same growing medium. I kept the containers covered in a clear plastic cup with some air holes again. This time I kept the same CFL about 8 inches from the top of the surface of the growing medium. My seedlings came above the ground quickly again in about 3 days. They looked like they were growing good for a few days again, but just like before, after about a week of being above the ground, they limped over and died. It was the same thing with the weal stems again. I even tried supporting them with a loose piece of wire and a toothpick, but like before the stems were so weak this didn't make much of a difference, and they still limped over. 
 
I only have ten seeds left, and this has costed me time and money. My water ph is ideal at around a 6, my temperature is at around 80 degrees f and my humidity should be ideal at around 55%. I also know that my perlite and coir isn't too moist, and I frequently check for this. I did not give them any nutrients either at this stage. I never had this problem with sprouts from my bag seeds, using backyard soil and just relying on the sunlight in my attic window. Only since I've started using coco coir, perlite and CFLs on hybrid seeds I've been having these problems. What could I be doing wrong?

 

Yes, usually after a week the seedlings will grow very well, then when I check on them at one point I would notice a a very weak, skinny point on the stem, and they just flop over. What is damping off?

 

The problem is I can't get seeds in my weed anymore, and as a result this seedless weed is much more expensive (like $325 an ounce). If I had success with my bag seeds in the past I there's not too much more I can do here, but I grew those different by using backyard soil, miracle grow, no ph checks, and just using the sunlight throughout the entire plants life, including the seedling stage. This worked and I had good buds, but I'm afraid to use this setup with expensive hybrid seeds, but I may end up doing this at this point anyways. There should be a universal ideal way to grow your plants for the first two weeks of the seedling stage though.

 

So does this mean my seeds, my water or growing medium is bad? Yes, that's what the stems looked like, someone pinched them.

 

 
My first attempt I did go with about 80% coco coir and 20% perlite, and they still died. I tried the higher perlite ratio after a grower on another forum told me that it sounded like I was having drainage issues, since coir holds water very well, so the roots may not be getting enough air. He apparently started his seedlings off with this ratio and had success with it so I followed his advice. I considered this advice because I'd read that during the seedling stage you don't feed them nutrients since they feed off of their first leaves, and that using nutes too early can kill them. I had also thought neither coir nor perlite have any nutrient value in them, which is why you need to start feeding them after the first two weeks. This is info I had gotten from other growers and grow advice sites.

 

 
I was told to put the seedlings in clear domes because at this stage they like higher humidity, and it prevents them from drying out. Someone thought my problem might be the seedlings drying out. I'd also read that many growers prefer to start their sprouts in an enclosed environment. If I put a fan on them I'll have to do away with the domes then. See why I keep getting frustrated  because I have so many people telling me to do different things. Maybe I'd be better off with bottled water, I was using filtered tap water. I'll try your suggestion though, and I still have several seeds yet, but I'm thinking of holding off for now and going with potting soil and perlite since I've heard this is easier than hydroponics. I could have the fan blowing on them and use a humidifier instead. I already have Dyna Gro for my soil nutrients. Hopefully once I cook the soil the mildew won't return. 

 

I was on my very last seed, but it was an unknown bonus seed that I got as an extra from that seed vendor. I germinated the seed in a wet paper towel until a tap root formed. Normally I don't do this but I had many older bag seeds that I wanted to try to germinate too, and out of desperation I had decided to germinate this seed the same way. Several of the older seeds had tried to open, but could not seem to develop a tap root. I did get one tap root to develop, but it never seemed to develop once it came above the ground. The last imported seed that I had I kept separate, and it developed a tap root after three days. 
 
I did something differently with this seedling, since it was my absolute last seed, and all of my other methods had failed. This time I had decided to go with soil, and I had a bag of miracle grow organic mix, and I mixed this soil with some from my backyard. I didn't add perlite because this soil mixture was already very chunky, and I actually had to water it more often than even the coco coir and perlite because it would dry very quickly. I also kept the seedling in a warm room by an open window where direct warm, humid air and indirect sunlight reached it. This seedling actually developed slower than some of my other ones, though the others would then die after one week to ten days. This one surprisingly made it to the two week mark. After two weeks it was at about five inches tall, with a set of well-developed leaves in sets of threes. 
 
I transplanted it to a five gallon nursery bucket, and used the same soil mixture, but this time I added about fifty percent perlite. I've kept the unknown breed and sex plant under four 150 watt 6500k cool white cfls for about four weeks after the seedlng stage. I cut the vegetative stage a bit short because the plant really started to grow very fast, like almost an inch every day, and my growing space is very limited. It has been about a week into the flowering stage, where I'm going 12/12 with light and dark cycles. I switched my lights to four daylight style 150 watt cfls to give the plant a more red spectrum light.
 
The plant is now at about 18 inches tall after about seven weeks of total life, and oddly it has already shown visible signs of its sex, which I know of since I had grown before. The wispy white hairs are very visible. I was very fortunate to have my very last seed germinate, and make it past the seedling stage. I was even more fortunate to get a female out of this. I'm pretty sure the genetics are good since it came from a respected seed vendor, and is likely some type of hybrid. It looks predominantly sativa since the leaves are longer, but they're huge. I had never seen bigger pot leaves in my life, and every subsequent set of leaves gets bigger than the previous. The newest set of sevens are actually the size of my hand, and I have average sized hands. The leaves are very long, but they're also very wide. It seems to be a more narrow and taller plant, and even spreading my lights out did not change this. I was wondering which type of strain it is. I don't have a decent camera currently but I'll try to post a picture of it when I get one.