Do I need nutrients in the first week of growing?

NO nutrients for the first 3-4 weeks in FFOF. That soil is already packed with everything the plant needs. Adding more will cause nutrient burn (yellow/brown crispy leaf tips).

Start feeding at 1/4 strength around week 4, then gradually increase. Less is more with cannabis nutrients.

The #1 beginner mistake is overfeeding. Cannabis is surprisingly good at finding what it needs in decent soil. When in doubt, just give plain pH'd water.

Wait until you see slight lightening of the lower leaves (the plant telling you it's hungry), then start at quarter strength. You'll usually see this around week 3-4 in FFOF.