No nutrients till the round smooth cotyledons start to discolour. And over watering can easily happen at this stage just a light application of water around the area of the stem but don't water the stem itself. Literally just a splash of water will due.
Up your temps and drop your humidity and get some air circulating around. It will dry out much faster. Then going forward be very gentle with the watering cuz your seedlings are just babies and are fragile at this stage.