How much did you wrap up? At least one "wall" of the run should be uncovered, with ample vents around the top of the others. I think a lot of folks overwinterize and it affects the ventilation throughout the entire area, so even if the coop hasn't been wrapped changing the airflow in the run may still affect the ventilation in the coop.
Even with bantams you need to think about ventilation in square feet, not inches. Since it's on the front page today...
https://www.backyardchickens.com/articles/repecka-illustrates-coop-ventilation.77659/ But the reality is it's very hard to add ventilation to smaller, squatter coops due to lack of wall space.