ppfd

if u are using normal soil (not coco) u should have sufficient nutrients for at least 3 weeks.

if it's soilless medium, yes. You need to give a full well-balanced diet with an overall concentration of 1.5-ish EC... YMMV. read and react to adjust formula as needed. 10% runoff in soilless is required. it makes buildup impossible. if it's soil - maybe.. .depends on many factors not mentioned.

Hey, i call your plants perfectly fine. They are "normal" sized for their age. Make sure to focus on the root development in these early stages, foliar growth will then naturally follow up. You can start adding fertilizer, just make sure to use very low doses maybe start with 1/4 of the concentration and work your way up.

No dont use any nutes yet! maybe after the third week u can slowly put some nutes in the water, they look good bro, mayb the soil is a bit to dry .. keep the soil wet (damp) so the roots can grow (as above so below, dont forget) goodluck!