Laura,
You have described the inquiry process for an activity on plant growth. If we frame it using the Framework for Inquiry outlined in this module you have introduced a prompt = What happens to a plant when…
The children then can share what they know as they wonder and explore – and exploring can include looking at the planned equipment for the activity so that they can make up their own starter question that is directly relevant.
I’d draw attention to fair testing, which is vital in this case, since “Each group of students planted seeds and varied one condition while keeping the others constant.” which sounds as if each group could compare to the other groups, which would be valid if the seeds that were watered, had the same amount of water, and each group had the same amount of soil, the same shape container, planted the seeds to the same depth etc.
I note that you had the plants growing from seeds – so there are two different processes under examination. Did any group find that their seeds germinated in darkness, but then the plant didn’t grow the same as others?
Depending on the type of seed you have, some will not germinate unless they are in darkness, so did you try scattering seeds on the top of the soil vs planting?
“and adjusting their hypotheses as necessary.” is the learning happening. As the children observed different growths they would revise their undertanding.