5 day old seedling curling up at leaves any advice on what could be the cause?

It's too hot, reduce the temperature, during the day it should be about 24-26 degrees Celsius, and at night about 20-17 and everything will pass, plus if the lamp is too low, growth may slow down, the lamp should be hung at a height of about 45-50 centimeters from plants. Everything will be fine. The main thing now is to reduce the temperature in the growbox.

"watered with a light misting" -- stop doing that. that is something that makes you feel useful but is the absolutely wrong way to water a plant. Coco/perlite, so it's a soilless context... 1) fertigate everytime with a well-balanced 1.3-1.5Ec diet and 10% or more runoff out the bottom. 2) allow top layer to start to dry, repeat. Even for a young seedling, having a healthy amount of nutes around the roots, even if unneeded initially, has positive impacts on the plant in the long-run. 1.5EC of a well balanced mix should not cause any problems, if it does, it's probabyl not 'well-balanced' and some component is too high/low. Get 10% runoff, religiously. this ensures that the level of nutes, even if slightly different than what you feed, remains consistent over time (no buildup is possible), which is the key. If consistent, this means you can simply adjust formula and almost immediately change ratios/concentration of nutes in the substrate and in a predictable and measured way. It also mean you can be significantly more confident that if you see any leaf symptoms it is 100% about your formula and not some buildup in the substrate. Diagnosing issues in a properly run soilless grow is infinitely easier, because there is only 1 thing to blame - the fertilizer you provide. Never partially water. Never neglect to get at least 10% runoff out the bottom. these are simple things to adhere to and doing so avoids a multitude of issues that result from poor fertigation habits. the runoff can be used for plants in the earth, but not potted plants. Toss down the drain, otherwise. What you see may or may not be caused by that, but eventually you will cause problems with your poor fertigation procedure This could be environmental. this could just be the first couple sets of leaves being fugly and the plant will grow out of it. The first sets of leaves are not always pretty even if it's a perfectly healthy and happy plant. If ther is any leaf curl, it's incredibly minor. I'd wait and see. You might be over-doting a bit... pretty soon you'll be treating it like a red-headed step-child.

Nothing wrong with her, she's praying which is a good thing, I would keep going what your doing and make sure you keep your temp and humidity in the proper range and you'll be GTG Keep the growing..

There IS nothing wrong here mate.

Hey there great start When the leaves curl up like that it's a good sig. Idk scientific term but alot of people say the leaves are praying. It's a good sign. Usually means there happy and could possibly be ready for slightly more light. If the leaves are "praying" at a much higher angle than they are now them that means they really want more light. I think your good at this point I would keep doing that your doing. Make sure to keep your humidity and Temps at a good range it will help your plants especially seedling

Seedling looks 100% ok. Misting is useless, water normally, it is almost impossible to over water in coco.