Clawing leaf on seedling

Probably from the leaf hitting the side of the cup. Pictures taken under blurple lights are pretty crap, next time you post pictures, try and take them under normal light, it makes life a lot easier for anyone trying to diagnose what is going on and add their opinion. Also, fill your cups right up next time - giving your seedling such a miserly amount of substrate to try and live in and establish itself, is bordering on plant torture! The poor roots would already be going around in circles, wondering how to escape the prison cell they are in! Surely there is no soil/substrate shortage in your part of the world, filling those tiny cups, (which in my opinion are waaaaaaaaaaaay too small for seedlings anyhow), right up will give so much more room for root growth, which translates to much more and much faster above ground growth. Getting your seedling happily established is an extremely vital stage of development and skimping on this part of the process is negligent, as your whole grow is depending on that seedling being happy and growing quickly, 2 things it can not do in half a coffee cup of soil. Try using proper gardening pots, black plastic ones are ideal and in a size of about 4inches wide and 5 inches deep, will provide plenty of room for root growth and your seedlings will grow much faster and more healthily too . And the best thing about the black plastic pots is, that if you look after them and wash them thoroughly between cycles, they will last many years, reducing garbage going to dumps and this keeps Planet Earth a bit cleaner. Hope this helps,...... Organoman.