Right-hander Jacob Turner pitched just 5 2/3 innings, while the offense couldn't conjure the big hit in a 4-3 loss to the Rockies in front of 20,191 at Marlins Park.
The team fell to 8-15 in August after closing out its 10-game homestand, 3-7. It embarks on a nine-game road trip following a day off.
"Really, the whole homestand we didn't play well and made a lot of little mistakes that ended up costing us in games," Marlins manager Mike Redmond said. "Like I said at different times in the homestand, we're not a team equipped to make a lot of mistakes, and when we do make mistakes they usually come back to haunt us. You saw that again [Sunday] and the last seven, eight, nine days of this homestand."
In a 3-3 game, Turner (3-5) surrendered the go-ahead run during a two-out rally in the sixth.
Nolan Arenado drove in Michael Cuddyer with an RBI double to left after Cuddyer singled to right. It would be the final pitch for Turner, who allowed four runs -- three earned -- on six hits with just one strikeout and one walk on 80 pitches (49 strikes).
"I felt like it's frustrating when the team comes back to tie the game and for me to get two outs in that sixth and give up back-to-back hits to score the game-winning run," said Turner, who last won July 10 against the Braves and now rides a four-game losing skid. "That's obviously probably the most frustrating thing that's sticking with me."
His wildness and Donovan Solano's miscue contributed to three Colorado runs in the second inning.
Turner fell behind the first three batters as Cuddyer walked and Arenado singled to center. A wild pitch advanced both runners into scoring position.
Ryan Wheeler then produced an RBI single to left. On Jordan Pacheco's lineout to second, Solano threw to first -- trying for a double play -- but the ball got away from Logan Morrison and bounced into the stands, scoring Arenado and moving Wheeler to third.
Jonathan Herrera added a sacrifice fly to deep right for a 3-0 lead.
Miami chipped away at the deficit on Justin Ruggiano's opposite-field solo shot to right with two outs in the bottom half of the frame. His 15th of the season came on a 2-2 pitch from left-hander Jorge De La Rosa (14-6).
Since snapping his 0-for-42 slump on Aug. 14, Ruggiano is 10-for-19 (.526) with three long balls, six runs and eight RBIs in seven games.
The Marlins tied the game at 3 off De La Rosa in the fourth, but failed to take the lead despite the first five batters reaching base to open the inning.
Giancarlo Stanton doubled off the wall in center before Morrison, celebrating his 26th birthday, drove him in on a soft liner. After Ed Lucas walked, Ruggiano collected an RBI single to center.
De La Rosa walked Adeiny Hechavarria to load the bases, but Koyie Hill grounded into a pivotal 5-2-3 double play. Turner struck out looking to end the threat.
"It's tough to give Nolan a day off, ever," Rockies manager Walt Weiss said of his third baseman. "We keep running him out there because he does stuff on defense to win us games. The double play was the ballgame, really, and he got the big hit on top of that. He was huge today."
Ruggiano's hit would turn out to be the last one for the Marlins, who picked up five -- one more than all of Saturday night -- through Sunday's first four innings.
Eleven runners were left on base by Miami, which included chances in both the fifth and sixth when a man stood at second with no outs.
On Christian Yelich's slow roller down the first-base line in the fifth, he collided with De La Rosa. The ball popped out of De La Rosa's glove and caromed into shallow right. Yelich ended up at second on the play.
Solano was called out on his bunt as the ball hit him as he left the box. Stanton reached on an intentional walk. Both Morrison and Lucas grounded into fielder's choices.
Reliever Adam Ottavino walked the first two batters he faced in the sixth, but Hill couldn't put down a sac bunt and struck out swinging. Pinch-hitter Greg Dobbs flied out to center against lefty Josh Outman and Yelich struck out swinging.
Ruggiano led off the eighth with a walk and moved to second on Hechavarria's bunt. Right-hander Matt Belisle forced Hill to pop out to third after his liner sliced just foul, and pinch-hitter Jake Marisnick struck out swinging.
The Marlins brought the game-winning run to the plate after Rockies closer Rex Brothers walked Solano with one out. Stanton struck out looking. Following a walk to Morrison that placed runners at first and second, Lucas grounded into a fielder's choice to end the game.
"I thought it was probably a different game if I get the sac bunt down in the sixth," said Hill, who entered the game with a personal-best .298 career average against the Rockies.
"Most of the time these games come down to fundamentals, and you win or lose ballgames. The team that out-executes the other is usually the team that comes out on top."