judging by the dark green appearance, I would venture to say you are nuting way too early.
Depending on strain... It's not the kind of green from too much N, it just looks more like a naturally dark green strain to me as apposed to the lime green strain often seen around, I've had strains like that in the past, mostly bagseed.
Cardinal rule of growing-no nutes in first three weeks of life. Even mild, they need zero and are very sensitive to the slightest dose, even 1/16th. they will grow out of it so either flush or not dont feed anymore nutes.
Good rule, no feeding for first 3 weeks.
But a lot of bought potting mix contains nutes already, which rarely actually harm your seedlings. If you want to be extra careful buy seed raising mix for seedlings and pot up into a 'stronger' potting mix later in life.
Careful with the watering though, just because the soil surface is dry doesn't mean it's dry throughout the root-run. Over watering is very easy when plants are young.
Two important things in ze basics of ze plant growing:
Root need water. But roots also need air!!! And if roots are surrounded by too much water, they cannot receive air!