Hi there, I am no expert but here is my take
Germination:
Jiffies look very moist! Even after watering. They can hold excessive amounts of water which can hinder germination or kill the seedling. 35-40ml of (luke)warm water per pellet to start with is more than enough.
Nutrients:
IMO yes it's too early... so I think you made the right call to stop with it :). The plant uses nutrients from its cotyledon leaves and the soil for 1 to (X amount) of weeks. Once the cotyledons start to yellow and die is a good sign that you should start to add some nutrients.
Of course there is stuff like root booster etc. which may be added at different times. However, 10 ml of grow nutrient is not what the plant needs now IMO.
For the rest don't be afraid to let the soil get a bit dry until watering. Maybe lower the light if they keep stretching as they are a little tall.
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