CBS News is stumbling under editor-in-chief Bari Weiss as both the “CBS Evening News” and “CBS Mornings” have fallen to troubling ratings lows, pointing to a deepening audience slump at the network. For the week ending April 20, “CBS Mornings,” co-hosted by Gayle King — who recently reupped with the network — drew just 1.8 million viewers, far behind NBC’s “Today” at about 3 million. Meanwhile, ABC’s “Good Morning America” stood at roughly 2.9 million, while delivering only around 310,000 viewers in the key 25–54 demographic compared to 639,000 for “Today” and 508,000 for “GMA.” Bari Weiss, editor-in-chief of CBS News, is facing mounting scrutiny as the network’s flagship broadcasts struggle in the ratings. CBS via Getty Images For that same week ending April 20, the “CBS Evening News” averaged just about 3.8 million viewers, far behind ABC’s “World News Tonight” at roughly 8.5 million and NBC’s “Nightly News” at around 6.1 million.…