It's overwatered see the big dark patch around the seedling? That seedling needs maybe a couple tablespoons of water and it looks like you have it a couple cups it's drowning from lack of oxygen. Give it way way way less water and start in a smaller container like a solo cup so at least if you over water it'll dry out faster. Number one killer of seedlings and young plants is over watering/ grower trying to do to much give let it grow or you'll baby it to death. It doesn't need watering everyday until it's huge I know you want to feel like you doing something but that'll kill it