The run is dry now.Is the water coming from outside, and dripping in? That will be a hole in the roof to fix.
If the water is not coming through the roof, it is condensation, which can be from a damp coop/run, or not having enough ventilation.
A damp area for the chickens to live in (day and night) can lead to mold, which can make them very sick. That's why they need a dry coop and run.
How cold is it there in the daytime, and nighttime now?