From a fellow grower: Grand Daddy Purple Autos and 10 Girl Scout Cookies Extreem Autos. All but 3 germinated. Not bad. I use the damp paper towel method. I do not have photos of this 1st grow. I planted them in coco-coir and perlite. Yes, the coco was prepared thoughtfully, rinsed thoroughly and buffered properly. The mixture was 50/50 coco and perlite. They came up but soon died though I watered them daily and did not let them dry out as instructed. One week later I planted the remaining 10 Girl Scout Cookies Extreme Autos. This time I put some quality potting soil in the upper fourth of the cups. They were doing so so but some started looking sad a few days ago so yesterday I transplanted them into larger pots with a mixture of coco, potting soil and perlite. The first grow was coco-coir and perlite only. In this specific case I was told to never let the coco dry out and to water daily. I will never use coco-coir without soil again. I will not water daily either. The ph of the runoff was much higher than the water going in. In that first grow I would often ph the water or Cropsalt/ water to 3 and the runoff was 8! One extreme to the other. I am now PHing to 6.2 or very near that but of course now I am using 50% soil in the mixture having just transplanted them in a last ditch effort to save what I can. The last ppm reading was 1251 but all has changed since then including the size of the pots and the medium. The soil looks wet in the photos because it had not dried completely from when it was mixed. It is at room temp and is mostly dry now. I will for sure be careful not to overwater. I am using, “Garden Rich Potting Soil…Great for container grown plants…Ideal for repotting…Ready to use”. I have had good results with it in the past. The light I use is an AgroMax LED RAW 550 watt and it is at its lowest output setting and about 4 feet above the young plants. I have it turned on 24 hours per day. This helps keep the temp in the 2’ x 4’ tent at about 71 degrees Fahrenheit. Humidity is about 55 to 60%. I am not using AC or other heat source and no exhaust until later in the grow/season. I do not plan to add nutrients until the plants need it later in the grow. This potting soil is plenty for these sad, little plants.
This stuff? 
Soil and Coco require 2 different pH levels. I am dealing with some of these exact issues right now. For the first 3 weeks, you can overwater in coco.
I just killed 10 plants from overwatering in Coco and I started in soil and transplanted to Coco and that also caused issues.
Here is the Proof of Death
These were all going on 6 weeks. Super stunted growth.
I would pick one medium and get it dialed in and then explore other options that suit you.
Coco pH 5.5
Soil pH 6.5
What I learned is once the coco has been rinsed and buffered with cal mag, keep them in a humid rich environment and do not water them unless the coco has visibly dried out. While the tap is growing, she will get the moisture needed from the RH. Once she starts putting out new true leaves you can start with 1/4 strength feeding at 10-20 ml depending on pot size.
Now I have started another bean in Coco/Perlite only and believe with mistakes made I have learned how NOT to do it.
Likely the problem here.
The plants look like they dried out or got sunburnt.
With coconut coir and perlite mixes, most people use a 70/ 30 mix (7 parts coconut coir and 3 parts perlite). The ratios are done by volume, not weight because perlite weighs next to nothing.
Perlite needs to be washed or wet before handling because it has a fine dust that can damage your lungs if you inhale it.
Baby plants (less than 1 month old) need 8 hours of darkness to rest and recover from the light. After a month or so you can increase the lighting times and reduce the dark times. I start my seedlings off under 20watt LEDs and after a few weeks I increase the light. A 550watt light unit at it’s lowest level might have been a bit much and dried the soil out too quickly. This would be possible with a 50/ 50 mix of coconut coir and perlite.
If there is too much moisture in the soil, the stems on the seedlings tend to change color and the plant will fall over and die. Too much moisture is caused by watering too often or having poor draining soil. The 50/ 50 coconut coir/ perlite mix you used should have provided excellent drainage and aeration to the roots, so damping off/ root rot is unlikely to be an issue, even when watering every day.
This has been debunked. Plants on 24/0 do just as well.
Who debunked it?
Don’t remember. It was some time ago.
Me, and basic scientific theory on C3 plants. They do not need any darkness except for to flower.
There’s not a lot of practical scenarios where I would suggest running 24 hour light, but cannabis plants will do everything they need to grow without any darkness. Just need to be aware that mols per day will increase without reduction in photons.
Here’s a little help for you, plant seeds after sprout in pure coco in a solo cup, it won’t dry out as fast as coco/perlite. I wet my coco same day I dropped seeds, next day they went in damp, not wet paper towels, next day into solos and under a dome, I don’t think I had to water them for first week, then just enough to keep coco damp and when roots hit bottom and spread, only then did I water to runoff. I actually did this for a couple weeks, until they were transplanted to bigger pots. When roots hit bottom of big pots, I started watering every day and still once a day. About to flip, so they might need two feedings, but I hope one will do them until auto pots take over next round.
I run mine at 24/0 for consistent warmth while in Solo cups. Once transplanted they go on 16/8 etc.
BTW those lights you coached me on building are awesome.
Bringing temp up or trying to veg with undersized light are the easily justifiable situations it may be good to run 24 hour light. Using hid bulbs is another as the constant heating and cooling is hard on them but they will stay on for a very long time if left on.
Glad you are still digging them! You’re probably not far from being able to justify a repower 
With the first grow if there was nothing but coco-coir and perlite and ph of runoff was coming out way high then the water/feeding going in then the coco-coir was not properly buffered.
I’ve no experience with coco-coir heavy soil mixes so I can’t offer much help with these 2nd ones.
I will say that coco-coir and perlite feed daily is the easiest way to grow but got to have quality coco-coir and proper preparation…