I'd change the lighting to 18/6. What are the daytime and nighttime temperatures? Make sure the thermometer is away from the lights though, so you can get an accurate reading.

Also, new plants like high humidity until they start developing multiple nodes. what is the humidity level like?

From your pictures though, they don't looked too stressed. They look good, not stretching too much. I've had plants that take about 2 weeks to get the first real node.