Seedling lean/stretch

Just get a little fan near her to increase airflow and that stem with strengthen in no time 💪

if you've been increasing light intensity... this could be part of the problem... too much light can cause a seedling to double-voer just as too much stretch can weakin the stem and it won't hold its own weight -- biggest difference is the color of the stem -- if pale/white-ish, it's most likely due to stretching. Your stem doesn't look like it's caused by stretching. Also, keep eye on resulting internode length -- an internode is simply the stem between 2 growth nodes. If there is no distance between growth nodes you end up with multiple sets of leaves popping out right near each other... it will look funky. this is also a sign of too much light. the opposite is too much stretch and both are bad. use a toothpick or something similar to keep it vertical / straight. it'll harden up over first 1-2 weeks and you can remove it at some point. trial and error.. .learn you rlight relative to your local environment... it won't be exactly the same as others, but will be similar. if you can find someone using same equipment, you can cut some corners by doing what they do to start, but still do a little trial and error to find the most you can give. initially they won't want much -- just give enough to avoid pale stems... any sudden grwoth and increase intensity... won't take long before they want it full bore (35-40 DLI for ambient CO2). DLI is an apples to apples measurement - regardless of size of garden our light cycle hours.. so you can compare 12/12 to 18/12 or photoperiod to autoflowers... worth a read -- daily light integral (DLI) -- simply about number of photons per day... whehther it receives it over 12 or 18 doesn't matter much as far as total phtosynthesis occuring in plant.

That is not stretching. Relax. The first push after it opens up is several inches then it will stop and start growing leaves. It’s natural to grow vertical fast like that so it can break the soil if it’s too deep. Only need to worry if it’s like falling over.