health New to starting seedlings…Got a some questions, pictures included

So I am new to growing and I have a couple questions that I have come across with my experiences. This post might seem scatterbrained but it is what it is.
My first and most burning questions is regarding a handful of jalapeño and stripey seedlings I started a couple weeks ago. I started them late for my area simply because I got the seeds late. All of my other peppers are already planted in the garden and I was wondering if since the weather is nice enough in my area for it, should I just start hardening off the 2.5 week old seedlings now so that I can complete their seedling growth (the next 4 to 6 weeks) outside? The reason I ask is just so that they will have better lighting (the sun instead of a 10,000 lumen LED 4 in away) and the soil will dry out better (really damage my seedlings from earlier this spring by overwatering and don't know if most of them will recover).
I was also wondering do peppers started indoors typically develop a purple stem as opposed to those started in nurseries?

Another situation:
I started most of my pepper seedlings in 1 to 3 inch pots and sittings in 10x20 trays sitting under 2 side-by-side perpendicular 10,000 lumen LED shop lights. However, I had two pepper that were started one week earlier than the others that were both started in 1 gallon pots and were on the outskirts of the lighting. All of the seedlings started out healthy but the leaves of the peppers in the gallon pots were larger and healthier looking and grew a lot bigger (more that just one week older growth) Eventually they all got sickly I think because overwatering but I am curious, do you think that the peppers in the gallon pots outgrew the others so well because they were started in bigger pots (more space, and less watering) or because the other peppers were getting too much light?

Also: I purchase the Neptunes harvest to fertilize my seedling. I used it once and when I went to use it the second time, a layer of mold was growing in the neck of the bottle and I didn't know if that was something to be worried about? My seedlings started going down hill about a week after starting to use fertilizer but I wonder if that is more coincidence. I was attempting to keep the fertilization at about half strength (eyeballing it). I am thinking of using a different fertilizer for seedlings next spring of anyone has any suggestions.

Companion planting:
How close to peppers do you usually plant companion plants (marigolds, chives, basil)? If you have two peppers that are 12"-18" apart, can you plant a low growing companion plant that won't compete for room (above ground) in between them, so about 6"-9" away, or will the companion plant compete for the peppers nutrients, diminishing your pepper crop?

Horribly, as I mentioned above, my peppers seedlings that started healthy, by about 4 weeks old, all of them started to have pale leaves (some plants leaves also becoming purplish), purple stems, upcurled leaves, and about half showed the crystallizations of edema. Many that had been topped, the lower leaf buds didn't start forming. And the leaves that were developing were really small. The least damaged peppers were the Jigsaws and Fish peppers but even their leaves were lighter and small. I think it was a perfect storm of problems that occurred at the same time: overwatering, moving them to a different part of the house that although still warm was more open and cooler than their initial location, and I increased the fan pressure on them to 24/7 (trying to compensate overwatering and fix edema). I was struggling at first determine if the signs were due to overwatering, over/under fertilization, or too much light but I think it was mainly the watering.

Here is some pictures of the progression of my seedlings (don't mind the non-pepper plants). Also just a disclaimer, this is a mix of hot and sweet peppers:

This was my Setup:

27-30 days after sowing: Looking good at first
Screenshot 2023-04-15 at 3.42.55 PM.png
Screenshot 2023-04-15 at 3.43.28 PM.png

2 Weeks later:This was when I think everything went wrong (had just moved their location 3 days earlier, fan was on them 24/7 (although on low power), and although probably a little overwatered I think they got really overwater while I was out of town)
You can see the major difference in growth between the two in the gallon pot and all of the other peppers.

11 Days later: (The purple glow is because I was worried I might have too much light so I took away one of the 10000 lumen lights and added a couple lower power multi-spectrum lights (thought the different spectrum of light might help with edema)

Last but not least, one week ago after planting my garden. You can tell which peppers came from my seedlings and which are from the nursery just off of color.
Screenshot 2023-04-15 at 3.47.26 PM.png

Once again, I know this has been as scatterbrained post. I have been on quiet the gardening rollercoaster with these peppers over the last couple months and it has raised so many questions. I appreciate any insight that anyone has for me.
I'd lean towards overwatering as your soil looks quite wet on some of your pictures. Also, your tomato plants are losing their lower leaves, pepper leaves are canoeing and your pepper + squash plants are yellownish (nutrients lockout?), all possible signs of overwatering...
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