Be careful not to over water and keep them propped up if they reach for the light and fall over. Try to get them as close to the light as you can so they don't have to reach. Any yellowing of a leaf at this stage is not good. Keep them damp but not soggy, no nutes until transplanted and given a little time to root in their new environment. One of the most common problems with seedlings is stem rot from keeping the grow medium to soggy around the base of the stem. You want them to have to dig deep for water to induce root growth.