Assuming you're not doing something kooky with your team (like making your worst pitcher the closer), I chalk up bad records in 1-run games to luck. Almost without fail when I notice a bad stretch in 1-run games, my team will turn things around and start playing better in the close ones. For example, in a 120M theme league that recently finished, my team had an 0-8 record in 1-run games just 27 games into the season; from that point on, they went 21-16 in 1-run games. I have a team in an OL right now that's 1-10 in 1-run games 50 games in; I predict by the end of the season we'll be a lot closer to .500 than .091 in the the close ones.