A number of broadcast programs hit ratings lows Tuesday night, as a challenging week continued for the big four networks.

TVbytheNumbers.com reports that NBC’s "Chicago Fire" slipped to a season low, based on Nielsen overnights for the key 18-49 demo, while "The Biggest Loser" equaled the season low it set a week ago. The two-hour "Loser" notched a 1.7 average, with "Fire" serving up a 1.8 — off two-tenths from last week.

An ABC program went even further into "dubious distinction" territory, as "Killer Women" fell two-tenths to a 0.7 average in the 18-49 demo — a distant third in the 10 p.m. hour and a number that matches the lowest for any Tuesday original on broadcast this season.

As bad as the numbers were for NBC and ABC, Fox’s results in 18-49 were even worse. "Dads" and "Brooklyn Nine-Nine" equaled their all-time lows, while "New Girl" and "The Mindy Project" matched their season lows.

"Dads" fell off three-tenths from a week ago in viewers 18-49, settling for a 1.2; "Brooklyn" slipped one-tenth to a 1.4; "New Girl" held steady to last week with a 1.6; and "Mindy" dipped one-tenth to a 1.2.

Coming out relatively unscathed was CBS, which won the night with steady numbers for its drama lineup. "NCIS" equaled last week’s 3.0 average in adults 18-49, "NCIS: L.A." matched its previous original’s 2.4, and "Person of Interest" came in with a 2.0, the same as last week.

For prime time overall, CBS averaged a 2.5 in the 18-49 demo to lead NBC (1.7), ABC (1.4), Fox (1.3) and Univision (1.1). CBS piled up a massive lead for prime time in total viewers, averaging 15.9 million to top NBC (5.9 million), ABC (4.6 million), Fox (3.1 million) and Univision (2.8 million).