Josh Zeid and Darin Downs (1-1) combined to allow three seventh-inning runs, and the Astros lost 6-5 to the Washington Nationals, who completed a sweep of the two-game interleague series Wednesday night.
"We haven't won in a couple days, and we were in position to win, and that's what feels bad," Zeid said.
Nate McLouth hit the go-ahead sacrifice fly to seal this victory. The Astros have lost three straight and four of five.
Scott Feldman became the fourth starter in that five-game stretch not to pitch past the fifth inning.
"Anytime you start to stretch it out, and now you're trying to get 12 or more outs out of those guys down there, it makes it very challenging," manager Bo Porter said of the bullpen.
Feldman grinded on a steamy evening, allowing two runs, six hits and three walks. He left with a 4-2 lead after throwing 103 pitches in five innings.
Dallas Keuchel, who started on Tuesday, also worked five innings - giving up four runs.
"Hopefully, from here on out, we can get a little deeper into games and give those guys a break," Feldman said of the Astros bullpen, which has an MLB-worst 4.72 ERA.
The Nationals stole a season-high five bases off the right-handed starter, who has allowed 14 steals in 17 attempts. But Feldman stranded multiple runners in the first, second and fifth innings.
"I felt fine, just missing a little bit down, stuff like that," Feldman said. "I was just missing my spots a little bit, and they were good at waiting me out and getting something up in the zone."
Jose Altuve singled twice, scored and walked to go 6 for 9 in the two-game series. Matt Dominguez singled in a pair of runs for the Astros, who scored four runs in the fourth off starter Gio Gonzalez.
Zeid gave up three runs while working an inning plus two batters. One of those two was Anthony Rendon, who led off the seventh inning with his 10th home run to cut Houston's lead to 5-4.
Zeid then walked Jayson Werth, and Downs gave up a single to Adam LaRoche - his only batter - that moved Werth to third.
"I had a job to do, come in and hold a lead, and I didn't do that," Zeid said. "I didn't get ahead of guys, I left balls up in the zone, and major league hitters are going to turn around and make you feel pretty bad."
Farnsworth induced Ryan Zimmerman to hit into a fielder's choice. Zimmerman beat the relay to first as Werth scored the tying run.
Ian Desmond doubled to put runners on second and third, and after Farnsworth intentionally walked Danny Espinosa, McLouth hit a fly ball to left field on the first pitch he saw.
Aaron Barrett (3-0) got one out for the win. Rafael Soriano earned his 15th save.
With Houston trailing 2-0 in the fourth, five straight Astros reached. After a walk and a hit batter, Jon Singleton singled to load the bases. Dominguez then lined Gonzalez's fastball to left field for a two-run single.
Jason Castro followed with an RBI double, and Jonathan Villar added a sacrifice fly to put Houston ahead 4-2.
The Nationals cut the deficit to one when Span's two-out double in the sixth scored Espinosa.
The Astros got it right back in the seventh. Robbie Grossman went from first to third on a single by Altuve and scored on Ross Detwiler's wild pitch.
NOTES: Houston RHP Brad Peacock (stomach virus) didn't make the trip to Washington. He will rejoin the team Thursday for the start of a four-game series at Tampa Bay. Houston RHP Collin McHugh (4-4, 3.03) will face RHP Chris Archer (3-4, 3.40) on Thursday.