Welcome to the grow!
Cotyledons (the two small circular leaves that first sprout from a seed) have enough energy stored in them to last slightly over a week.
With that being said, I would give them the first nutrients at a low level at one or two weeks old. I would defiantly look up the feed chart on whatever nutrients you are using and start with the light feeding. Looking at your grow diary, the soil could be a range of nutrient level so it’s really up in the air. I personally will feed my plants a very light dose at one and two weeks old. Had great success doing this.
It doesn’t take much for these little guys to grow in the first two weeks, they are generally just trying to expand their root system for the first two weeks.
When you water for the first week and every week after, you need to adjust your pH of the water to 6.1 - 6.5. Water as needed when the soil is starting to dry out. That could be every 2-3 days. When my girls are that young I do every other day with 1 cup for the first week.