today I checked the soil on her, the top layer has...

Hi, slow down your watering, the plant cant drink so much, a seedling in that stage need 10-30 cl ( 10-30 ml ) in 24 hours. Overwatering brings you a lot of issues and pests. Let her dry for a week minimum and then go on watering ( if she lost the weigh of the water)I give 2 cups of water to a grown up plant 6-7 weeks old . Try to keep an wet/dry circle . Between the waterings the layer of the soil should be knuckedeep (2cm) dry... Underwatering a plant can handle very good, overwatering is a common mistake that brings you a lot of trouble.

Growers usually start in solo cups and then pot up as needed, because it makes watering easier; it's really easy to overwater when using big pots from the beginning if you don't know how much water is actually needed. For a seedling, a cup of water (200 cc or 7 oz), should last 5 or 6 days, depending on your environment (temperature and humidity); so you see 2 cups is already too much for a recently sprouted seedling, wait 10 days before watering again, the idea is to force the seedling to develop a strong root zone while hunting for water. Next time you use 1 cup of water again and when you notice that the pot dries faster, lets say 2 or 3 days, then you double the amount to 2 cups, let the soil dry again and use the same amount, when again it takes 2 to 3 days to become dry, you again double the amount. The soil should not stay wet more than 4 to 7 days.