Post transplant plant help.

Hey everyone! I was hoping you could help me figure out what happened to two of my seedlings after transplant so when I redo them I can avoid this issue. All of the other plants are doing wonderfully and these two are the same type. I kind of got lost on which are which, so I THINK these MIGHT be cucumber? 😱 If anyone knows different, please feel free to correct me!!

Please note that in the picture the soil looks dry, but it's actually just mostly the top layer and I let it dry out more because I was worried I was over-watering them.

A little about the environment:

Heat- The ambient temp is set to 60° (although it was 57° originally). This temp will fluctuate because it's just our general heater for our house. Since the plants like it warmer, I positioned the plant wall where the seedlings were originally… between two heater vents that point up. This way they get the air circulation and also get the warming effect. In addition to that, we've put a small oil heater near the front of the plant wall.

Lights- The lights aren't super ideal atm as we're still doing the setup, but there's a full spectrum light shining on them for however many hours we've got it set at (same as when we were growing the seedlings- I kept most of the setup the same). It's 845 lumens and less than a foot from one and less than 2 from the other. This bulb was recently switched from one that might've been more powerful because it looked brighter… but when they got switched we found that it was more likely the lamp itself causing the appearance of change.

Air flow- I've got a bathroom vent fan that I put on occasionally just to be sure they get some additional air flow. It's what I had on hand and I point it over the plants rather than directly on.

Watering/feeding- This also hasn't changed. I am generally around them all day so on the usual day I tend to lightly water the individual plants that have dried out more. Once a week I tend to do a deep watering (since these were recently transplanted with freshly made dirt, the dirt… which was the same general formulation as the OG… was pretty wet already, so I haven't done any real deep watering yet- it's just getting to the point where I would and will). When I water, there's nearly always a tiny bit of fertilizer in the water so there's always abundant food.but not so much it'll negatively impact anything. I use this same water for all of my plants and none of them have complained. The water I use is warm in order to give the soil warming cycles.

Location- It's really not been long enough that this should matter, but I planted with companion plants, so unless I SERIALLY misidentified (even if it were to end up being bean or squash it would work with the other seedlings)… that shouldn't impact it.

More info- They both had nice, healthy, thick stems. One was very short, so I buried up to the first leaves. The second I had left stem out… it was looking dark (my husband said they had originally looked like that, and I hadn't noticed, so I took his word for it), but also got softer. I subsequently buried the stem deeper. (Keep in mind this was less than an inch difference.) The plants just got kind of soft and sad at first. The other has only just developed the brown spot. Just today they've got a bit of a crispy feel to them. It's been less than a week, but more than a day or two. It's possible they're damping off… but I also wonder if for some reason there's some serious transplant shock going on.

Any suggestions you can give would be much appreciated!!! Thank you!!