The ideal humidity for them is around 50 to 60 percent.
During the vegetative stage, when your plants are growing lots of thirsty leaves, the need for moisture spikes and they thrive in humidity levels up to 70 percent.
Use the photone app. You should be around 400 ppfd. But I don't think the light is the problem. This looks to be a problem of over-watering. Or maybe the plants are still getting acclimated after the transplant. You did the right thing spraying the leaves instead of watering.
What strains did you get? And from where? Some autoflowers stay little runts. But others get nice and big. I think it depends on conditions and genetics. Mostly conditions probably.
The drying and curing process is just as important if not more important than the growing process itself. If you don't have a designated tent with climate controls for drying you can use totes or cardboard boxes to slow down the drying process.