The Covid-19 self quarantine has been rather expansive and longer than many were expecting. The CW, out of caution for their actors, crew and others, suspended production on their shows. Batwoman and The Flash have 22 episode season orders. As of now, roughly 19 of those episodes have been filmed. Supergirl is in a different situation. Their season is only 20 episodes long and has filmed some of the finale, possibly enough to edit it to a full episode. Regardless, in an effort to give more time to the shows and possibly let them get caught up, the CW edited their schedule so that the shows that are finished don't run out.
Today, The CW shared the return dates for the four continuing Arrowverse shows. The Flash and Legends (airing on Tuesdays) will return April 21st. Batwoman and Supergirl (airing together on Sundays) will return April 26th. Until then, no new episodes will air. With shows having between 4 to 7 episodes left to complete a season, this unexpected hiatus might give production enough time to catch up if the social distancing works and production can begin again in May.