There can be following reasons for their wilting.
1) Do not give them more than 6 hours of direct sunlight and if you are growing under grow lights put them for 16 hours a day.
2) Keep rotating your microgreens so that they get the light equally on all sides or use a grow light at the top to equally distribute the light on all sides.
3) Water the baby plants only when the soil seems dry; don’t overwater them.