I use nutes from the first day. Others wait a week or two. When they are small like that, you may want to water less and more often. Those little roots do go very far yet, so if you may be losing a lot of water just to evaporation rather than going to feed and grow the roots.
IMHO you could start veg nutes now at 1/3 strength with no problem.
IMHO you could start veg nutes now at 1/3 strength with no problem.