Too many variables

So... I'm basically a drunken gardener over the winter, starting my long germinating peppers and stuff mid winter, but as noted in my introduction post, I bit off a large lump of that spark plug and I am suffering because of it.

To date, I have alwaysbstarted my pepper seeds in actual dirt, under a humidity dome with a heat mat and i have had no troubles. This year I went high tech. Mylar grow tent, full spectrum LED lights, soil thermometers, carbon exhaust filter, evacuator fans, mineral wool starter cubes... the works. Hurah technology.

This is also the first year i have seen this happen: https://ibb.co/tPyWys9 - and it happened almost overnight. These little guys were early to sprout, and all looked great until they didn't and I have no idea what to start with to troubleshoot.

Any hints or diagnostic questions would be appreciated because i dont knownwhere to start!
 
Too close to light I think. Looks like burn from moisture on leaves under hot lamps....never used LED's so not sure if that can happen but that's what it looks like to me.
 
Thanks for the tip. I've turned off 4 of the 8 bulbs. Hopefully that helps.
I would need to build a new table to get the seedlings farther away from the lights but I guess that will be next if things dont start improving.
 
It would be much better to add more space between your LEDs and your plants than to diminish the light ouput. Take a look at the owner manual (or on the manufacturer website) and you should find infos about how far this particular lamp should be from your plants at different stages of growth. My two cents...
 
I typically think the lights are too close when I see the leaves canoeing like that, and that may be the or a main factor, but I'm going to suggest there may be other issues.  You mention you've always grown in soil before, so maybe this is your first work with rock wool and you're getting the watering timing down still. 
 
The picture looks like the roots may be saturated. I'd remove the cubes, shake (not squeeze) out the excess moisture, then dump any water remaining in the germination chambers before re-positioning the cubes.   For future watering, I suggest watering more lightly rather than saturating the cubes because the cubes have nowhere to drain off excess moisture in those plastic pockets.  Water lightly, and let the cubes distribute the water evenly through the cube themselves in the several minutes after you water.  Otherwise, you may have nutrient uptake issue and or water/oxygen problems with the roots leading to root rot.  Root rot can make it appear as though the plants are under watered because the roots can't function properly to uptake the water. So more water, more rot, etc...  After you water, if you lift the cubes out and any water remains in the cup or you shake them and a significant amount of water comes out, then IMO they've been over watered.
 
Another likely contributing factor could be humidity in the domes.  If you take plants out of those super humid domes they won't be adjusted to the drier air outside.  The higher-up growth will transpire water too quickly and you'll get that classic canoeing.  So, either take the sprouts out of the chambers/domes immediately upon sprouting or, if you leave them in longer, transition them out gradually over a couple/few days by progressively opening the dome more to air flow.
 
My take, back the lights off, dial the water back, and be gradual in removing the domes.  Also, if you have fans blowing directly on the plants, use either oscillating fans sweeping over the plants for a very limited time during each day or fixed fans circulating air generally all day during the light cycle, but never fixed fans pointed directly at the plants.  I do both, with a fixed fan tracking the light schedule (but not blowing directly on the plants) and an oscillating fan on a timer running for a couple 30m clips each day during the light cycle and sweeping over the plants. A fixed fan blowing continually directly on the plants will also increase the transpiration demand and can cause canoeing of the upper leaves. 
 
Just my 2 cents.
 
Good luck!
 
CaneDog said:
Another likely contributing factor could be humidity in the domes.  If you take plants out of those super humid domes they won't be adjusted to the drier air outside.  The higher-up growth will transpire water too quickly and you'll get that classic canoeing.  So, either take the sprouts out of the chambers/domes immediately upon sprouting or, if you leave them in longer, transition them out gradually over a couple/few days by progressively opening the dome more to air flow.
I always take the new sprouts and put them in a new open top tray. I find this kind of damage when the water condensates on the leaves when the dome is on.
 
Awesome tips. I've got a drain pan on order now, and I'm checking for the light distance.

I left the domes off a few overnight and they looked pretty dry so I gave them a soaking, but i was not thinking about the fact that they can't drain. Hopefully they recover and keep on truckin till spring.
 
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