The cursed

What’s the EC of the soil in ms/cm ? It should be written on the bag. Looks like it’s a bit too high for seedlings. I suggest to start seedlings in a light mix for seedlings and clones.

once that clears up, can tackle any nutrient issues.. until then the too intense light could be exacerbating a problem that might not occur otherwise. looks like you need more perlite or similar in that substrate too - improves drainage qualities. maybe, start in a smaller pot and transplant to larger pot when size of plant warrants the increased pot size too. otherwise, it's difficult to irrigate properly. 50/50 for soil / drainage amendment - by volume, respectively. 70/30 for coco+perlite (or similar), because it holds less water per volume. if you water a small circle around plant, make sure that saturation goes all the way to the bottom, or you are promoting superficial roots. if the top is moister than the bottom of substrate, which will happen with bad irrigation habits, the roots turn upward.. they are far less useful when they expose themselves to light, lol... not even roots long after that. just useless stems along surface of substrate. also, a healthy wet-dry cycle occurs when doing it right... reduces risk of pests and pathogens. don't pick a volume to give.. the dynamics of the soil, size of pot determine this. when the plant fits the pot size, you saturate the entire thing -- never leave a dy pocket. overwatering or droopy leaves should not occur while doing this. if it does it is a sign you need better drainage qualiteis in the substrate. frequency of irrigation should not be an issue if sticking to good wet-dry cycle.. wait for top 1" to dry. repeat. keep it simple, stupid (KISS principle)

your nodes looks tightly stacked on top of each other.. .too much light, too early... you stunted it. there should be an internode between nodes... it is part of the anatomy. use its resulting length to help choose light intensity -- can adjust height, dimmer or hours per day to influence this. if you change hours of day, just stay in safe range for bloom or vegetative phases. if autoflower, this matters not. reduce light and within 5-7 days should be exhibiting better behaviour... be ready to increase light later on, as a mature plant can handle more than a seedling can. you just jumped the gun a bit. i find there is quite a bit of variance in what a seedling can handle.. with some plants you may not have this problem while doing the same things... it's fust that seedling was more robust than others and nothing you can predict. so change your process for early stages to be more inclusive. just beacuse 'it worked before' doesn't mean it's best or optimal.