Over-watered seedlings are almost always stunted. They’ll typically need watered only twice in a solo cup the first 10 days or so. At that point the seedling should almost be big enough to come out of the solo cup within 2 weeks with a decent root system.

Solo cups are fine for clones but not plants.

Intersex traits are 100% genetic that can be induced by environmental conditions. The environment doesn’t cause the traits, they were always there.