Could you please help me figure out why her leaves...

She is way to small for day 16. Without a diary can't say but she doesn't have the proper growing conditions.

High VPD means the air is dry and warm, leading seedling to lose water faster than they can absorb it. This can cause wilting, stress, and potentially stunted growth in seedlings, as they are particularly vulnerable to water loss until they are in veg. The big fat lip on your pot doesn't help fill soil to top when you can.

I'd wager you blasted it with too much light too soon. Nodes are tight, growth has slown.. slightly pale... Back off but if it starts to stretch you backed off too much. The older nodes will always be a bit too close compared to any new growth, but should start to space out a little bit. Resulting internode length is your guide for light intensity. If seedlings are given too much, you can stunt their growth. Just be ready to provide more when they show hint of too much stretching.

poor little thingy check ur Ca ppm bs it looks like Ca excess and NPK lockout

Hey Growmie, She looks a bit stressed for day 16, droopy and pale leaves usually point to environmental issues or overwatering. Since your VPD was off until recently, that likely caused excess transpiration and slowed growth. Aim for 0.4–0.8 kPa VPD with ~75°F and 65–75% RH. Also, be careful not to overwater, seedlings don’t need much, and wet soil can suffocate roots. The pale color could be early nitrogen deficiency or pH lockout (check that it’s around 6.0–6.5). If you’re in an inert medium, consider starting ¼ strength nutes. Once your environment is dialed in, she should bounce back soon.